Bernie Sahlins, seen here in 2001, nurtured generations of comedy talent at Chicago’s Second City. (Thomas Englund/The Second City/Associated Press)

Bernie Sahlins , a comedy impresario who co-founded the Second City troupe that nurtured such talents as Alan Arkin , John Belushi , Dan Aykroyd , Bill Murray, Gilda Radner and Joan Rivers, died June 16 at his home in Chicago. He was 90.

The cause was pancreatic cancer, said his brother, Marshall Sahlins.

Mr. Sahlins’s influence on American theater — in particular, sketch comedy — cannot be overstated. So many “Saturday Night Live” performers were Second City veterans that Mr. Sahlins once jokingly suggested the theater bar entrance to SNL producer Lorne Michaels, lest Michaels raid all of its talent.

In the 1960s, actors Alan Alda and Peter Boyle and stand-up comedians David Steinberg and Robert Klein performed in Mr. Sahlins’s Second City club in Chicago. An aspiring playwright named David Mamet once worked as a Second City busboy.

“Bernie’s track record discovering future Hollywood megastars was unmatched,” comedian and Second City veteran Tim Kazurinsky told the Chicago Tribune. “He probably was responsible for the greatest revolution in American comedy.”

Mr. Sahlins and producer Andrew Alexander expanded the Second City brand to Toronto in the early 1970s. The Toronto casts included Aykroyd, Eugene Levy, Andrea Martin, John Candy and Martin Short.

Mr. Sahlins later helped develop the television show “SCTV,” which ran on Canadian television and later on NBC and parodied contemporary programming with shows from the world’s smallest network in the fictional Melonville.

Long after Mr. Sahlins sold his stake in the business, Second City continued to serve as a training ground for entertainers, including Stephen Colbert and Tina Fey. The organization now has touring companies and schools to teach comedy performance.

Mr. Sahlins founded the Second City — as it was originally called — in 1959 in a former Chinese laundry on North Wells Street in Chicago. His partners were two other theatrical veterans, Paul Sills and Howard Alk.

All three had struggled financially with earlier theatrical ventures and were thinking smaller — a coffeehouse venue devoted to satirical comedy and improvisational theater. They took the name from a New Yorker column by A.J. Liebling that spoke derisively of Chicago theater.

“We had a golden opportunity,” Mr. Sahlins told the New York Times in 1999. “McCarthyism had chilled everything, and comedy was a lot of mother-in-law jokes. All you had to do was go out on stage and say ‘Eisenhower’ and everybody had an orgasm. It just wasn’t done.”

A typical Second City revue consisted of sketches created through improvisation but later polished and scripted with the show’s director. Improvisation also had a place in the finished program, often through audience suggestions that sometimes took a sketch in a new direction. The company got by with the barest of sets and props — a few chairs and a piano.

“We wear our characters lightly and dress them lightly,” Mr. Sahlins once told Time magazine. “Put on a pair of glasses and you’ve got a businessman.”

The improvisation evolved from theater games created by drama teacher Viola Spolin, who was Sills’s mother. Sills would eventually leave the company and start his own improvisational troupe.

Given his theatrical background, Mr. Sahlins was most comfortable with a scripted show. “Improvisation is not a presentational form, except in small doses, or as a game,” Mr. Sahlins said. “It’s a tool.”

The belief led him into a bitter conflict with his director, Del Close, who regarded improvisation as an art from. When Close was on his deathbed in 1999, Mr. Sahlins conceded that for one day — and that day only — improvisation was an art form.

Bernard “Bernie” George Sahlins was born on Aug. 20, 1922, in Chicago, where his father was a doctor. The younger Mr. Sahlins majored in math at the University of Chicago and later ran a tape recorder business.

His involvement in professional theater began in 1953 when he, Sills and David Shepherd produced plays for the Playwrights Theater Club, a short-lived repertory company that included novice performers Mike Nichols and Elaine May.

In 1955, Sills and Shepherd started the Compass Players, an improvisational comedy group considered the precursor to Second City; meanwhile, Mr. Sahlins produced shows at the Studebaker Theater on Michigan Avenue.

Mr. Sahlins’s notable Studebaker productions included the Chicago premiere of Samuel Beckett’s “Waiting for Godot.” A staging of the Greek classic “Lysistrata” with Nichols and May was less notable. One Chicago critic called it “the worst production in 2,000 years.”

The Studebaker struggled with its finances until 1957. Two years later, Mr. Sahlins started Second City.

After selling Second City to Alexander, producer of the Toronto company in 1984, Mr. Sahlins co-founded the International Theater Festival of Chicago with his wife, Jane Sahlins.

Survivors include his wife of 44 years, Jane Nicholl Sahlins, and a brother, Marshall Sahlins, both of Chicago. His first marriage to Fritzi Sager ended in divorce. A daughter from his first marriage, Lee Sherry, died in 2012.

Mr. Sahlins thought the relationship between the audience and the troupe was essential to its success.

“We’re not joke-tellers here. The audience and the actors are all about the same age (18 to 35), and we speak to their concerns,” Mr. Sahlins once said. “Our humor comes from audience identification.”

He added, “When we’re cooking, people are saying, ‘Yes, oh, yes.’ It’s the joy that comes from seeing the truth.”