Addison is the youngest child of the Montgomery family, daughter of Bizzy and The Captain and younger sister to Archer. Originally from Connecticut, she hails from a privileged background, with Addison owning $30 million trust fund, but her family life was far from perfect. Her adulterous father used his time spent with her as a pre-tense for his many extramarital affairs, and Addison was forced to lie for her father to her unassuming mother. This led to a certain disdain for her father which, in her adulthood, she would learn to be unfounded after she discovers that her mother actually cheated on her father, partaking in a lesbian relationship. Her parents stayed together to maintain the image of her a perfect family and to keep Addison and Archer happy.
She followed in the footsteps of her father and became a doctor, attending Columbia, and it is here that she would meet her future husband Derek Shepherd, as well as her best friend Naomi. Aside from a brief interest with Naomi's future husband Sam which would go forgotten soon enough, Derek and Addison married and both graduated and went on to complete their residencies alongside Sam and Naomi. Their marriage was for the most part happy and Addie was liked by most of Derek's family, especially his sister's Nancy and Amelia, but his mother never liked Addison. Addison and Derek would eventually relocate to New York where they both began their practice alongside Derek's childhood best friend Mark Sloan.
Her relationship with Derek eventually becomes strained and she sleeps with Mark. When Derek discovers her infidelity he leaves New York for Seattle and Addison tries to move on herself. She and Mark develop a relationship which is tested when Addison falls pregnant. She aborts the child, realizing she doesn't want a family with Mark, and heads for Seattle to win Derek back.
Grey's Anatomy, Season 1Edit
Grey's Anatomy, Season 2Edit
With Derek's relationship with Meredith in disarray he turns antagonistic towards Addison who remains in Seattle at Richard's request to help with a difficult case. Addison eventually tells Derek that she still loves him and wants to fight for their marriage, which makes a resistant Derek question if he is really ready to get over Addison. She presents him with signed divorce papers and tells him that the choice over their future is in his hands and, despite Meredith's desperate attempt to win him back, he chooses to stay with Addison and give their marriage a second chance. Addison soon accepts Richard's offer to officially join the staff of Seattle Grace and moves into the trailer with Derek. Their marriage is, at first, strained by their past indisrections with Meredith and Mark but Addison tries her best to reconnect with her husband. Derek tries to fight for his marriage but remains distant, eventually confessing to Addison that Meredith wasn't a fling but that he was in love with her.
Addison and Derek both continue to try and make a life for themselves in Seattle as Derek and Meredith attempted to be friends, leading to Addison and Derek becoming the owners of Meredith's dog Doc when she was unable to care for it anymore. When a 'Code Black' was declared at the hospital due to an explosive situation in the E.R Addison was forced to deliver Bailey's unborn child under the tense circumstances with George by her side. Addison and Derek then faced pressure when Mark arrived in Seattle trying to persuade Addison to return to New York and give their relationship another try, quickly realizing she never told Derek about their attempt to be together. Addison ultimately chose to be with Derek and remained in Seattle. The pressure continued to be felt in the Shepherd's marriage but Addison received an unexpected surprise when treating a patient forced Derek to see that he wasn't there for Addison in New York, being mostly absent. He then told Addison he was just as responsible for her adultery as she was. Addison faces a stressful time when Alex Karev persuades a patient to sue her, resulting in her assigning Karev to her service indefinitely.
Her marriage begins to improve, but their sex life continues to be a shadow of it's former self. Addison is soon delighted when their sex life is reignited, but is unaware that Derek is simply pushing too hard due to his own heartbreak over learning that Meredith is now seeing their vet Finn Dandridge. After Derek lets his feelings get the better of him regarding Meredith, Addison becomes aware of his true feelings leading to a public confrontation between the two. In spite of this, Derek and Addison attend the hospital's prom together - but she remains unaware that Meredith and Derek slept together during the event leaving the state of her marriage unknown.
Grey's Anatomy, Season 3Edit
Addison discovers that Derek and Meredith slept together when she finds her panties in the pocket of Derek's tux and struggles with the end of her marriage. Addison takes the day off from her surgical duties to tackle her grief but regretfully turns to Mark for comfort who flies back to Seattle to be with her, devastating Derek. Addison remains insistent that she doesn't want to be with him but sleeps with him several times. Moreover, Addison is stunned when Mark makes his move to Seattle permanent, making it hard for her to remain in Seattle professionally. Addison's divorce to Derek is finalized and they part amicably until he learns of her prolonged relationship with Mark. He is first hostile until he decides to try his best to put his anger behind him. Believing he was served his time, Addison released Alex from her service but the interest he has developed an neonatal surgery keeps them working together somewhat as he balances his interest in Addison and Mark's specialties. Her close working quarters with Alex result in a near kiss between the two, which is quickly brushed off, although Addison continues to be attracted towards him.
Conflict arises between Mark and Addison non her would-be due date making Addison remember the side of Mark that she liked and the side she wanted to be with before. After the Ferry Crash disaster, Addison gives Mark a deal: sixty days without sex and then they'll be a real couple. Mark succeeds in completing his end of the deal, while Addison doesn't sleeping with Alex. Mark, however, tells her that he messed up believing she shouldn't have to feel bad about not wanting to be with him. However, when Addison tries to pursue a relationship with Alex he shuts her down wanting nothing more than sex from her.
Feeling lost and alone in Seattle, Addison heads to L.A where she reacquaints herself with Sam and Naomi, who now run a well care practice. She goes to L.A to fulfill her one remaining dream - becoming a mother, but Naomi delivers devastating news when she reveals to Addison that she can't bear children. Feeling desolate, Addison struggles with her new feelings of directionless until Pete Wilder, a doctor at the practice, forces her to realize she isn't old or died up. Naomi reminds Addison that there's an office waiting for her if she wants it but Addison chooses to return to Seattle but keeps Naomi's offer in mind. Addison, who previously joined the race for Chief of Surgery, returns to Seattle trying to cope with the news of her infertility. When she learns that she hasn't got the position of Chief, she begins to question if there's a future for her in Seattle.
Private Practice, Season 1Edit
Addison arrives in L.A, deciding to take Naomi up on her offer but initially feels out of place to Oceanside Wellness when she learns Naomi didn't tell anyone of her hiring and, as such her new colleagues Pete, Violet and Cooper aren't very receptive. She develops a flirty, antagonistic relationship with Pete and is equally irritated by his womanizing as she is intrigued by him. She eventually begins to see a different side to him which results in them sharing a kiss and planning a date. Pete, however, stands her up and she ends their attraction on friendly terms, knowing that she has to work with him. During this time Addison rises to acceptance among her new colleagues, becoming closer to Violet and Cooper as well as Sam and Naomi. She then attracts the attention of Kevin Nelson, a cop and a friend to one of her patients, who eventually asks her out on a date. Addison remains unaware that, while on her date with Kevin, Pete showed up at her house to try win her back but her moving on saw the end of their flirtatious relationship.
Addison would later return to Seattle for a complex neonatal surgery and was forced to realize how much had changed in her absence. She was stunned to learn Meredith and Derek had separated, and urged Meredith not to let him get away. She also told Richard to fill her position, admitting she had found happiness in L.A.
Private Practice, Season 2Edit
After returning to L.A, Addison and Kevin had their date, but she doesn't hear much from him afterwards. Her mind is sidetracked regardless when she learns that Naomi is keeping the practice's financial troubles from her colleagues and she and Sam form a coup, destroying Addison and Naomi's friendship. Addison eventually hears from Kevin, who is not a SWAT team member and didn't call her as he was training for it, and their relationship begins. Addison soon becomes the practice's director when the rest of the staff vote her in, unexpectedly for Addison. As her relationship with Kevin progresses, she is forced to take a leadership role within the practice and makes the decision to sell the fourth floor, space with Sam and Naomi kept for future expansion of the practice which stateliness their financial troubles. However, Charlotte King buys the space and opens a rival practice. The arrival of Addison's brother Archer brings about the vast differences between Addison and Kevin's backgrounds. However, when Kevin is shot on duty Addison takes him in and begins to care for him but this isn't enough to save their relationship as Addison begins to question where they're heading.
Addison tries to work through her issues with Kevin while fighting her attraction to Pacific Wellcare oncologist Wyatt Lockheart which culminates in a kiss between the two. Addie keeps this from Kevin, who can tell that she's hiding something and when she comes clean they break up. Archer then returns to town and begins dating Naomi, which angers Addison. However, her feelings are put into perspective when she discovers Archer has a brain tumor and has come to say goodbye to her. After he has a seizure, she takes him to Seattle where Derek operates after discovering it wasn't a tumor but parasites in his brain. Archer survives but proves that he hasn't changed when he cheats on Naomi and subsequently leaves L.A.
Addison then develops an attraction to cardio doctor Noah Barnes but is devastated to learn that he is married to her patient Morgan Gellman. Addie and Noah's mutual attraction causes problems as she attempts to do the right thing, but this is compromised when she learns that Noah and Morgan's marriage was fractured before she fell pregnant. Noah offers to leave Morgan for Addison and they nearly sleep together, but are interrupted by the news of Morgan's labor forcing Addison to realize that she can't break apart their family.
Private Practice, Season 3Edit
Addison's personal issues are sidelined when Violet is found clinging to life but Addison manages to save her life, all while trying to put Noah behind her and cope with Noami's defection to the rival practice. She is forced to face up to her feelings for Noah when Morgan confronts her and Addie realizes that she didn't do the right thing by not sleeping with Noah, because he fell in love with her regardless. She grows closer to Sam and they develop romantic feelings for each other but both try to pretend they are still friends. Addison is then plagued by the arrival of her father The Captain, who wants another chance with his daughter and gradually their relationship improves until she learns that he slept with Violet. Devastated, she confronts her father who then demands her mother Bizzy comes to L.A and tells her daughter the truth which Addison soon discovers is that her mother is in an extramarital lesbian relationship. With her views of her family turned upside down she tries to sleep with Sam, who tries to do the right thing and turns her down.
Mark soon arrives in Seattle and he and Addie sleep together as she tries to come to terms with her mother's sexuality and this illicited jealousy in Sam. After they kiss again, Sam decides he wants to pursue a relationship with Addison but she is unable too, not wanting to hurt Naomi. Sam is hurt, but even more so when Addison's longing to be with Sam and her inability have him lead her to develop a sexual relationship with Pete.
Initially, Addison hides her from her feelings for Sam through the sex but eventually develops feelings for Pete and grows attached to his son Lucas. She and Pete decide to try their relationship for real as she becomes a mother figure for Lucas. Naomi also learns of Sam and Addison's attraction and is devastated, leading them both to try and put it behind them.
The arrival of Amelia Shepherd forces Addison to realize she's taking second best and that she really loves Sam, but when Violet returns and tries to resume her role as Lucas' mother Addison struggles. She eventually lets go of Lucas for his own good and accepts her feelings for Sam. After a car crash endangers Maya's life Addison operates and saves her, and she mends her relationship with Naomi, but the sudden death of Dell afterwards devastated her. Taking Sheldon's advice in the wake of tragedy, she decides to do what makes her happy and begins a relationship with Sam.
Private Practice, Season 4Edit
Addison and Sam keep their relationship secret from everyone, but must soon come clean to Naomi who is devastated. While saying that it isn't the end of her friendship with Addie, she temporarily leaves L.A and Addison and Sam begin their life together. It soon becomes clear that Addison is in the relationship for the long haul and wants children with him but Sam soon realizes she doesn't want this, as he already is a father. Addison's relationship with Sam also develops as a consequence of Charlotte's rape as Addison turns to him for comfort. Naomi soon returns, seemingly more at ease with their relationship but her return as Addison continues to wrestle with her desire to have a child. Addison was then stunned by the arrival of Bizzy in L.A with her mistress Susan who's ovarian cancer was threatening her life. Bizzy ordered Addison to save Susan's life but when Susan died Bizzy blamed Addison. However, Bizzy soon saw the error of her ways and apologized to Addison for the first time. Addison later returned to her hotel room and found that Bizzy had committed suicide.
Devastated about her mother's death she returned to Connecticut and, under her mother's orders, kept her suicide a secret claiming she died of a heart attack (although Charlotte saw through her lies). A grieving Addison returned to L.A but soon discovered that Sam had kissed Naomi in her absence as their relationship had suffered as a consequence. After Addison learned the truth Naomi turned on her stating that her relationship with Sam will always be worth more than Addison's. When Addison suspected she may be pregnant the differences between her and Sam were brought to the forefront and she asked him whether he was ready to commit to her, and to having a child with her. Addie is hot.
Later, after Callie Torres' car crash, Addison flew back to Seattle to help ensure the survival of Callie, Arizona and Mark's child, benching Lucy Fields in the process. She succeeded and Callie and the baby survived.
Upon returning to L.A, Addison found that Sam was still bot ready to give her an an answer to her ultimatum. When he is ready to answer, they realize they want different things and decide to separate but keep this a secret from their friends so as not to ruin Charlotte and Cooper's wedding day. Now without Sam by her side, Addison begins to feel increasingly isolated as she is also without Naomi and the future of the practice remains in jeopardy as a consequence of Violet's confidentiality lawsuit. She and Naomi eventually rectify their friendship, only for Naomi to leave Los Angeles, and Addison's isolation continues. At her therapists request, she tries something new and spontaneously begins dating a man and they agree to not share their names or details. When he asks her to come to Fiji with him Addison realizes she's running away from her problems and heads home to lead Oceanside Wellness into a new era and to reunite with Sam, telling him that having him and baby don't have to be mutually exclusive as long as he can love her with her baby.
Private Practice, Season 5Edit
Addison and Sam's recollection is quickly challenged as Addison begins actively pursuing her dreams of having a child, especially when her chosen fertility doctor turns out to be none other then Jake Reilly, the man with whom she tried to flee to Fiji with. She starts IVF treatments and learns that she has 4 viable eggs. Further along, she is completely unable to choose a sperm donor because none of them are "right". She revisits her past and cheating on Derek, and feels guilty all over again for what she did to him all those years ago.
Addison also starts to unravel the depths of Amelia 's problems. She meets her boyfriend Ryan and confronts Amelia about her issues. So the entire practice throws Amelia an intervention, but that plan shatters to the ground. After a tragic event with Amelia, Addison takes her to a rehab facility.
On the other hand, Addy is now on her last shot at IVF. She has her last two embryos implanted and will not try again if it fails. It unfortunately does, so Addison turns to adoption. Sam moves out so that the Social worker will have a better chance of approving of the situation and
Private Practice, Season 6Edit
Derek could not get over her cheating so decided to stay with Meredith
- After leaving Grey's Anatomy and appearing in Private Practice on a regular basis, Addison has appeared in the Grey's Anatomy episodes "Piece Of My Heart", "Before And After", "An Honest Mistake", "Blink" and "Song Beneath The Song"
- Addison was introduced under the name Addison Montgomery-Shepherd, a name which she held until her divorce to Derek was finalized in "Oh, The Guilt". At which point she reverted to her maiden name of Addison Montgomery.