Derek arrives at Seattle Grace Hospital as the new Head of Neurosurgery from New York City. He is a Bowdoin College graduate and attended Columbia University College of Physicians and Surgeons alongside his childhood best friend Mark Sloan and ex-wife Addison Montgomery and Private Practice characters Naomi Bennett and Sam Bennett. Derek was a student of Chief Webber and was enticed to come with an "offer he couldn’t refuse" – the position of Chief of Surgery, which Derek eventually turned down. He specializes in highly complex tumors and conditions of the brain and spine and came to Seattle Grace with a reputation for taking on "lost causes" and "impossible" cases that most of his peers would turn down. As an attending he is both well-liked and feared — well-liked by patients and his scrub nurses for his compassion and gentlemanly bedside manner and feared by interns and residents who are intimidated by his reputation and high standards. He is passionate about his job and has been known to expel staff or remove interns and residents (or at least threaten them) from his service for being disrespectful about patients or if he deems their attitude to be detrimental to his patient's well-being.
Derek first meets Meredith Grey at a bar, only to find out that she was an intern at Seattle Grace Hospital. They begin to have feelings for one another and it causes some awkwardness at work, particularly after her supervising resident Dr. Miranda Bailey discovers their relationship. Her housemates and fellow interns George and Izzie both antagonized her for some time as they felt she was using her relationship with Derek, an attending, to further her career but they change their opinions of Derek and accept his presence after he moves into her place, which has been dubbed a "frat house". He generally tolerated them despite his dislike for having to share his living space, especially with interns who worked under him. While most of his family members accepted Meredith, his sister, Nancy, particularly disliked her and repeatedly called her "the slutty intern"; as of season 9 she still refuses to speak to Meredith or acknowledge her as her sister-in-law. His mother Carolyn approved of her as she felt Meredith's grey perspective of life complemented Derek's tendency to see everything in black and white.
A private person outside the hospital, Derek's background was generally a mystery for the first season and source of speculation amongst his colleagues due to his suddenly leaving an established and highly respected practice in New York City to move to Seattle In the season 1 finale, his past eventually catches up with him when his estranged wife Addison Montgomery moves to Seattle and is offered a position by Chief Webber, shortly followed by his childhood best friend Mark Sloan, who joins Seattle Grace as the new head of plastic surgery. Derek and Addison attempt to repair their marriage but later acknowledge that their marriage should have been ended a long time ago and that Meredith was his true love. Since their divorce they have remained on amicable terms, with Addison even admonishing Meredith for breaking up with Derek in season 3. In the Private Practice episode "Ex-Life" he finally tells Addison that his mother never liked her in the first place. He admits to Meredith that Addison cheating on him with Mark was partly his fault as he was an absentee husband. Addison eventually leaves Seattle for a private practice in Los Angeles, spawning the spin-off Private Practice. In the season 8 episode "If/Then", in which Meredith dreams of an alternate universe where her mother never had Alzheimer's, Derek and Addison are still married but their strained marriage and Derek's disillusionment causes his career to stagnate and earns him the nicknames "Bad Shepherd" and "McDreary" due to his poor attitude and Addison still cheats on him with Mark.
Derek is offered the job of Chief of Surgery for the second time after the board wants to oust Dr. Webber. Derek, being faithful as a friend to Richard, wants them to consider keeping him somehow. During the merger of Seattle Grace with Mercy West their relationship sours as Derek disagreed with Richard's handling of the merger and Richard begins to display uncharacteristic behavior, which had not gone unnoticed by his fellow surgeons. Derek learns from Meredith that the Chief has since resumed drinking and feels forced to have him removed as Chief of Surgery. Having mixed feelings about Richard, Derek offers him an ultimatum: go into rehab and possibly pick up where he left off after, or quit completely.
In seasons 3 and 4 the relationship between Derek and Meredith hits a rocky patch and they dated other people for some time. His plans to propose were ruined by a series of unfortunate events in season 5. In the season finale, they were supposed to marry but let Alex and Izzie, who had just been diagnosed with stage 4 cancer, take their place. Due to their tight schedule, they instead informally marry and Derek writes down their "promises" on a post-it note. They legalize their marriage in season 7 in order to adopt Zola, a young African orphan Derek treated for spina bifida. However, they consider the post-it note to be their legitimate wedding and referred to each other as husband or wife even before legalizing it. They briefly separate after Meredith tampers with his Alzheimer's trial, jeopardizing her career and tarnishing Derek's reputation. Zola is taken away from Meredith after a social worker finds out she is not living with Derek. Derek becomes distrustful of Meredith in the OR so they agree that Meredith will not work in neuro anymore or talk about neuro at home for the sake of their marriage; since then, in later seasons, Derek have often griped about how his subsequent interns and residents – mainly Lexie Grey, Shane Ross and Heather Brooks – did not quite measure up to Meredith. The social worker comes back and announces they are the official parents of Zola. As Meredith is near the end of her fifth year of residency, she and Derek are torn between staying at Seattle Grace Mercy West or leaving for Boston where Derek would work at Harvard while Meredith would be at the Brigham and Women's Hospital.
Following his rescue from the plane crash that killed Mark and Lexie, Derek learns that he may only regain eighty percent of his hand's function. He comes to terms with the fact that his career as a surgeon may be over and is grateful that he is alive, in light of the deaths of his best friend Mark and sister-in-law Lexie. However, when head of orthopedic surgery Callie Torres (Sara Ramirez) tells him a more risky surgery could give him back full function of his hand or reduce its function if it goes wrong, Derek agrees to the surgery. He accepts the possibility that he may never hold a scalpel again. His hand recovers well and Torres clears him to return to work, but it is only weeks later that Derek feels he is ready to operate. Derek, Callie and Jackson decide to do nerve transplant for his hand. Meredith, newly pregnant with their second child, goes behind his back and calls his sisters so they can donate a nerve to him. Lizzie (Neve Campbell, Derek's younger sister, agrees to donate a nerve and the surgery is a success.
Derek and Meredith's marriage is strained after he accepted an invitation from the President to participate in the Brain-Mapping Initiative. He went back on his promise to her that he would not add to his current workload in order to devote time to their two young children and allow her the chance to establish her career as a full-fledged attending. Eventually he was offered a position at the National Institutes of Health in Washington, D.C., but Meredith puts her foot down and refuses to leave her hometown and uproot their young family. His youngest sister Amelia (Caterina Scorsone) takes over his position at Grey Sloan. Meanwhile, he and Meredith fight bitterly on and off over whether they should move. After a bad argument, he accepts the job in the heat of the moment and leaves for Washington. While there, he and Meredith talk things out over the phone and come to a mutual conclusion that they both did not want to end their marriage. He tells her that just being with her, raising their children and operating on patients was more satisfying than "saving the world".
In season 11 Derek suffers an accident while driving to the airport for his final trip to Washington, D.C. He is able to hear and process auditory input, but unable to speak. He is recognized by Winnie, one of the victims of a crash he assisted in earlier, who tells the surgeons that their patient's name is Derek and that he is a surgeon as well. The hospital he was taken to was understaffed and his head injury was not detected quickly enough by the interns on duty that night. Although the neurosurgeon on call is paged multiple times, he takes too long to arrive and Derek is declared brain dead. Police arrive at Meredith's door and take her to see Derek, where she consents to removing him from life support. He is now deceased. At the time of his death, unbeknownst to him, Meredith was pregnant with their third child. She gives birth to a daughter whom she names Ellis after her mother.
Derek was mentioned or referenced to a number of times in season 12 as the other characters struggle to cope with his sudden death. In the episode "My Next Life", Meredith has a flashback of their first ever surgery together when the patient Katie Bryce returns to the hospital with a brain aneurysm. Amelia took his death especially hard as he was the sibling she was closest to. At the end of the season, prior to her wedding to Derek's long-time colleague Owen Hunt, she goes on a nervous rant about how Derek was supposed to be the one to give her away, him having given away their three other sisters at their weddings.
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