Jerry Adler saw Zero Mostel dress up as a woman and Kate Hepburn ride an open-air construction elevator to yell at noisy workers. He was there when Carol Channing opened in “Gentlemen Prefer Blondes” and Rex Harrison first took the stage as Henry Higgins.

Adler, 77, has pretty much seen it all. He spent well over 50 years in show business, starting as an assistant stage manager on Broadway and ending as a director. He’s worked with the likes of Sir Laurence Olivier and Angela Lansbury. And at an age when the rest of the world is getting ready to slow down — heck, most of them have already moved to Florida — he accidentally started a second career as a character actor.

In just the last year or so, he’s appeared in several motion pictures, including “Prime” (with Meryl Streep and Uma Thurman) and “In Her Shoes” (where he kissed Shirley MacLaine).

But the role that clearly defines his career is Herman “Hesh” Rabkin, Jewish adviser to Tony Soprano on “The Sopranos.” Adler parlayed a brief cameo in the show’s pilot into a recurring role.

As the show’s aficionados know, Hesh was Tony Soprano’s father’s best friend and partner in the mob. “When Tony’s father died, Hesh became kind of Tony’s mentor and close friend,” Adler explained.

Within the world of gangsters, Hesh is a beacon of honesty. Unlike Tony’s Mafia buddies, there’s no duplicity with Hesh. Tony trusts him, and perhaps because of that there is not the slightest vestige of anti-Semitism from his crew. Though rival families call him “the Jew,” it is usually used as an adjective, not a pejorative.

The role, like the series, was created by David Chase. In fact, it was Chase who got Adler the “Sopranos” job — Chase was a writer on “Northern Exposure,” where Adler had a recurring role as Rabbi Schulman.

Adler’s acting career began in the same kind of it’s-not-what-you-know-but-who-you know fashion. In the early ’90s, he worked as a stage manager for a series of television soaps. An actress, aware that he knew a casting director searching for a female lead in a film, asked Adler to intercede on her behalf. He did, as a favor, but the casting director cast him instead (though, of course, not as the female lead). That was in a Joe Pesci movie, “The Public Eye.”

“I was actually surprised,” he says. “I’d never acted before. I’d never entertained the idea of acting. It was an unusual thing. But I was getting ready to retire from the production end anyway. So it became kind of interesting.”

There followed a series of television and film roles, usually as a Jew: Bert Mandel in an episode of “Brooklyn Bridge,” Lenny Greenman in “Quantum Leap” and Police Commissioner Gould in “Spin City.”

The truth of the matter is that Adler has a Yiddishe punim (“Jewish face”) — and yes, he says, “I understand what that means, because of my grandparents.”

Looking Jewish “helps you in some areas and curtails you in others,” Adler says. “I played Italian, I played Greek.” In what may be the strangest bit of casting, he played a Roman Catholic cardinal on an episode of “CSI: Miami.”

Adler grew up in Brooklyn. His father, Phil, was manager of the Old Group Theater, founded by Lee Strasberg, Elia Kazan and Stella Adler, among others. The theater was mixed up in the communist hysteria of the early 1950s, and it was there that Adler says Mostel dressed as a woman.

“They dressed him up in all kinds of costumes at the end of the show so he could get out the theater and they wouldn’t serve him papers.”

After graduating from Syracuse University he worked behind the scenes on and off Broadway. His first show was “Gentleman Prefer Blondes,” and he followed that with hits such as “My Fair Lady” and “Annie.”

He was stage manager on “Coco,” starring Katherine Hepburn who had to sing a soft lullaby during the second act. However, a building was going up across the street, and whenever Hepburn sang on Wednesday matinees, all the audience could hear in the theater was the jackhammers and other construction noise.

“She came to me and said, ‘Why don’t you go over there and tell them to stop work while I sing my lullaby?’ So I went over there, and they thought I was insane. They said, no way,” Adler recalled.

“Well, I told her. She went over there and got into one of those elevators and stopped at every floor. And don’t you know it, she got them to stop. When she was about to start singing, I’d go out the stage door and whistle, and for the entire run of the show, they’d stop work until I came out and whistled again.”

Adler was raised in a Jewish household that was observant, but became less so after his grandfather passed away. “I was a bar mitzvah, but kind of drifted away from it.”

Yet some of those lessons remain. He’s turned down parts that “were not acceptable to me: a Shylock-y Jew and a Jewish pedophile. These are parts I wouldn’t do.”

Ironically, his second wife comes from a more traditional family and he now celebrates all the holidays with them, in Teaneck, N.J.