An actor, improviser, writer, and teacher, Close had a prolific career, appearing in a number of films and television shows. He was a co-author of the book Truth in Comedy along with partner Charna Halpern, which outlines techniques now common to longform improvisational theater and describes the overall structure of “Harold” which remains a common frame for longer improvisational scenes. His favorite framework for comedic storytelling was the structures of Wagner’s Ring Cycle.
Around this time, Close also worked with John Brent to record the classic beatnik satire album How to Speak Hip. The album became a prized record for DJs worldwide, and was one of Brian Wilson’s favorite comedy albums.
In 1960, Close moved to Chicago – which was to be his home base for much of the rest of his life – to perform and direct with Second City. Close was fired from Second City due to his substance abuse and spent the latter half of the 1960s in San Francisco, where he was the stage manager for The Committee theater, toured with the Merry Pranksters, and made light images for Grateful Dead shows.
After returning to Chicago in the early 1970s, Close was hired again to direct at Second City. He also performed and directed the Second City show in Toronto in 1977. Over the next decade he helped develop many of today’s leading comedians. Acolytes of Del Close have gained prominence in the field of comedy with astounding frequency. At any given time, roughly a quarter of Saturday Night Live’s cast has been composed of his former trainees.
Close spent the 1980s and 1990s teaching improv, collaborating with Charna Halpern in Yes And Productions, while slowly succumbing to emphysema. But he remained active. During this period, Close acted in several movies, including Ferris Bueller's Day Off, where he played an English teacher. He also co-authored the graphic horror anthology Wasteland for DC Comics with John Ostrander, as well as co-wrote several installments of Grimjack's backup feature Munden's Bar. Finally, along with Charna Halpern he co-founded the ImprovOlympic Theater.
Legend has it that Close's last words were, "I’m tired of being the funniest person in the room." Before passing away, Close requested that his skull be given to the Goodman Theatre for use in Hamlet productions, on the condition that he should receive credit in the program as Yorick. However, in 2006 it was revealed that an alternate skull was given to the Goodman instead. In honor of Del after his death, his former students the Upright Citizens Brigade created The Del Close Marathon.
The Delmonic Interviews includes interviews with: Charna Halpern (co-founder of Chicago's iO), Matt Besser (iO's The Family; Upright Citizens Brigade), Rachel Dratch (iO; Second City; Saturday Night Live), Neil Flynn (iO's The Family; NBC's Scrubs), Susan Messing (iO; Second City; Annoyance Productions), Amy Poehler (Upright Citizens Brigade, Saturday Night Live). The film was shown at several national improv festivals, including the 2004 Chicago Improv Festival, the 2004 Phoenix Improv Festival, the 2002 Del Close Marathon in New York City, and the 2006 LA Improv Festival.
The book has been adapted into a screenplay, and as of 2006 Harold Ramis was attached to direct the script, although it does not appear that the movie will soon be made. Ramis would like Bill Murray to play Close.
In 2007 Eric Spitznagel wrote an article in the September issue of The Believer magazine reflecting on Close's life and his propensity for story-telling. In 2008, Kim "Howard" Johnson's full-length biography of Close, "The Funniest One in the Room: The Lives and Legends of Del Close" was published. Johnson himself was a student of Close, and remained friends with Close until his death. In 1994, Howard co-authored "Truth in Comedy: The Manual of Improvisation" with Close and Charna Halpern.