After graduating from Syracuse University with a Bachelor of Fine Arts degree in Musical Theatre in 1983, Sorkin spent much of the 1980s in New York as a struggling, sporadically employed actor. He found his passion in writing plays, and quickly established himself as a young promising playwright. His stageplay A Few Good Men caught the attention of Hollywood producer David Brown, who bought the film rights before the play even premiered.

Castle Rock Entertainment hired Sorkin to adapt A Few Good Men for the big screen. The movie, directed by Rob Reiner, became a box office success. Sorkin spent the early 1990s writing two other screenplays at Castle Rock, Malice and The American President. In the mid-1990s he worked as a script doctor on films such as Bulworth. In 1998 his television career began when he created the comedy series Sports Night for the ABC network. Sports Night's second season was its last and in 1999 overlapped with the debut of Sorkin's next TV series, the political drama The West Wing, this time for the NBC network. The West Wing won multiple Emmy Awards, and continued for three more seasons after he left the show at the end of its fourth season in 2003. He returned to television in 2006 with the dramedy Studio 60 on the Sunset Strip, about the backstage drama at a late night sketch comedy show, once again for the NBC network. While Sorkin's return was met with high expectations and a lot of early online buzz before Studio 60's premiere, NBC did not renew it after its first season in which it suffered from low ratings and mixed reception in the press and on the Internet. His most recent feature film screenplay is Charlie Wilson's War.

After more than a decade away from the theatre, Sorkin returned to adapt for the stage his screenplay The Farnsworth Invention, which started a workshop run at La Jolla Playhouse in February 2007 and which opened on Broadway in December 2007.

He battled with a cocaine addiction for many years, but after a highly publicized arrest he received treatment in a drug diversion program and is reported to have recovered. In television, Sorkin is known as a controlling writer, who rarely shares the job of penning teleplays with other writers. His writing staff are more likely to do research and come up with stories for him to tell. His trademark rapid-fire dialogue and extended monologues are complemented, in television, by frequent collaborator Thomas Schlamme's characteristic visual technique called the "Walk and Talk".

Sorkin was born in Manhattan to Jewish parents, and raised in the wealthy suburb of Scarsdale, New York. His mother was a school teacher and his father a copyright lawyer; both his older sister and brother went on to become lawyers. Sorkin took an early interest in acting. Before he reached his teenage years, his parents were taking him to the theatre to see shows such as Who's Afraid of Virginia Woolf? and That Championship Season. At that age, Sorkin did not always comprehend the plot of the plays; nevertheless he recalls enjoying the sound of the dialogue.

Sorkin attended Scarsdale High School where he became involved in his high school drama and theatre club. In eighth grade he played General Bullmoose in the musical Li'l Abner.

In 1979 Sorkin attended Syracuse University. In his freshman year he failed a class that was a core requirement. It was a devastating setback because he wanted to be an actor, and the Drama department did not allow students to take the stage until they completed all the core freshman classes. He returned in his sophomore year determined to do better, and graduated in 1983 with a Bachelor of Fine Arts degree in Musical Theatre.

"I don't want to analyze myself or anything, but I think, in fact I know this to be true, that I enter the world through what I write. I grew up believing, and continue to believe, that I am a screw-up, that growing up with my family and friends, I had nothing to offer in any conversation. But when I started writing, suddenly there was something that I brought to the party that was at a high-enough level."

After graduation, Sorkin moved to New York City where he worked odd jobs ranging from delivering singing telegrams, driving a limousine, touring Alabama with the children’s theatre company Traveling Playhouse, handing out fliers promoting a hunting-and-fishing show, to bartending on Broadway at theatres such as the Palace Theatre. One weekend, while house sitting at a friend's place he found an IBM Selectric typewriter, started typing, and "felt a phenomenal confidence and a kind of joy that [he] had never experienced before in [his] life."

He continued writing and eventually put together his first play Removing All Doubt which he sent to his old theatre teacher, Arthur Storch, who was impressed. In 1984, Removing All Doubt was staged for drama students at his alma mater, Syracuse University. After that, he wrote Hidden in this Picture which debuted off-off-Broadway at Steve Olsen's West Bank Cafe Downstairs Theatre Bar in New York City in 1988. The contents of his first two plays got him a theatrical agent. Producer John A. McQuiggan saw the production of Hidden in this Picture and commissioned Sorkin to turn the one-act into a full-length play called Making Movies. His reputation as a playwright was quickly gaining stature on the New York theatre scene.