Mark first appears in season two , introduced as a highly respected otolaryngologist sub-specialized in plastic surgery and the childhood best friend of neurosurgeon Derek Shepherd ( Patrick Dempsey ) . In his first appearance , he flirts with Meredith Grey , and Derek punches him in the face . Derek explains that Mark had an affair with his wife , Addison ( Kate Walsh ) while they were living in New York . Mark travels to Seattle , intent on convincing Addison to return with him , but his offer is rejected and Derek declines to renew their friendship . Mark returns during season three at Addison 's drunken behest , but she again rejects him once sober . Undeterred , Mark sells his successful private practice ( which he previously shared with Derek ) and takes over the plastics program at Seattle Grace Hospital . During Meredith 's morphine rampage , Mark finds out about his nickname McSteamy which was given to him by her during his first trip to Seattle back when he attempted to get Addison back and earn Derek 's friendship back . It is later revealed that Mark has at some point slept with all of Derek 's sisters . Mark has a brief fling with Addison 's friend , orthopedic surgeon Callie Torres ( Sara Ramirez ) , and develops a friendship with Derek 's girlfriend , intern Meredith Grey ( Ellen Pompeo ) . It is revealed that after Derek left New York , Mark and Addison continued their relationship for two months , during which she conceived and aborted his child . Just weeks after moving to Seattle he quickly observes that Derek 's true love was Meredith and tries to convince Addison that her marriage with Derek was over . Mark enters into a sixty - day abstinence pact with Addison , agreeing that if they can remain celibate for that time , Addison will give their relationship another chance . Addison ultimately breaks the pact by having sex with intern Alex Karev ( Justin Chambers ) , and soon thereafter departs from Seattle to work in Los Angeles .

Question: when does sloan come into grey's anatomy
Answer: season two