Morse, known for his gap-toothed boyishness, started his career as a star on Broadway acting in musicals and plays before expanding into film and television.

Morse acted in his final stage role in the Broadway revival of the newspaper comedy The Front Page from 2016 to 2017.

Morse attained a career resurgence playing Bertram Cooper in the critically acclaimed AMC period drama series Mad Men from 2007 to 2015.

He portrayed Dominick Dunne in the FX limited series The People v. O. J. Simpson: American Crime Story (2016).

[8][9] Upon graduation, he left home for New York City to fulfill his ambition of becoming an actor, joining his elder brother Richard who was already studying acting at the Neighborhood Playhouse.

[10] Morse earned multiple nominations and wins for Tony, Drama Desk, and Emmy awards over a period of five decades.

During this time, he took television roles in The Alcoa Hour, Alfred Hitchcock Presents, Naked City, The Play of the Week, and The Jonathan Winters Show.

[13] Morse gained stardom for portraying the young 1960s New York City businessman J. Pierrepont Finch in the 1961 Broadway production, Frank Loesser and Abe Burrows musical, How to Succeed in Business Without Really Trying.

Crowther especially noted his performance, writing "Seeing Mr. Morse in close-ups, as those wily expressions cross on his face and those wicked designs of Pal Joey gleam in his Horatio Alger-character eyes, is better than seeing him on the stage".

That same year, he acted in the television series That's Life, which attempted to blend the musical genre with a situation comedy centered on newlyweds "Robert" and "Gloria" (played by E. J.

[25] Morse appeared in dozens of TV shows,[26] including Alfred Hitchcock Presents and The Twilight Zone.

[6] In 1987, Morse appeared in the film The Emperor's New Clothes, which starred Sid Caesar and was part of the Cannon Movie Tales series.

[29] Morse made his return to Broadway portraying author and socialite Truman Capote in the one man show Tru (1989), earning rave reviews for his performance as well as the Tony Award for Best Performance by a Leading Actor in a Play and the Drama Desk Award for Outstanding One-Person Show.

In 2002, Morse was cast as the Wizard of Oz in the San Francisco run of the Stephen Schwartz musical Wicked at the Curran Theatre, and acted opposite Idina Menzel and Kristin Chenoweth.

He was regularly nominated for a Primetime Emmy Award for Outstanding Guest Actor in a Drama Series as a result of his performance in 2008, 2010, 2011, 2013, and 2014.

[9][33] The series creator Matthew Weiner originally cast Morse in part because of his reputation on the stage, including his iconic role as social climber J. Pierrepont Finch in 1962’s How to Succeed in Business Without Really Trying.

Morse was cast as journalist Dominick Dunne who covered the 1994–1995 murder trial of O. J. Simpson for Vanity Fair in the critically acclaimed Ryan Murphy created limited series The People v. O.J.