Pollack died of cancer Monday afternoon at his home in Pacific Palisades in Los Angeles, surrounded by family, said publicist Leslee Dart. Pollack had been diagnosed with cancer about nine months ago, said Dart.
Pollack, who occasionally appeared on the screen himself, worked with and gained the respect of Hollywood's best actors in a long career that reached prominence in the 1970s and 1980s.
"He'll be missed terribly," Clooney said.
Last fall, he played Marty Bach opposite Clooney in "Michael Clayton," a drama that examines a law firm's fixer. The film, which Pollack co-produced, received seven Oscar nominations, including for best picture and a best actor nod for Clooney. Tilda Swinton won the Oscar for supporting actress.
Pollack was no stranger to the Academy Awards. In 1986, "Out of Africa" a romantic epic of a woman's passion set against the landscape of colonial Kenya, captured seven Oscars, including best director.
In accepting his Oscar, Pollack commended Meryl Streep, who was nominated for best actress but didn't win.
"I could not have made this movie without Meryl Streep," Pollack said. "She is astounding - personally, professionally, all ways."
Over the years, several of his other films, including "Tootsie" and "They Shoot Horses, Don't They?" got several nominations, including best director nods.
Pollack's movies frequently had some of Hollywood's top actors: "Absence of Malice" with Sally Field and Paul Newman, "The Yakuza" with Robert Mitchum, "Three Days of the Condor" with Robert Redford, and "The Firm" with Tom Cruise, among others.
"Having the opportunity to know Sydney and work with him was a great gift in my life," Field said in a statement. "He was a good friend and a phenomenal director and I will cherish every moment that I ever spent with him."
Before winning acclaim as a motion picture director, Pollack had his first taste of success as a director on TV, reports CBS News reporter Steve Futterman. He directed episodes of Ben Casey, The Fugitive and The Defenders.
In later years, he devoted increasing time to acting, appearing in Woody Allen's "Husbands and Wives," Robert Altman's "The Player," Robert Zemeckis' "Death Becomes Her," Stanley Kubrick's "Eyes Wide Shut."
Pollack's recent producing credits include "The Talented Mr. Ripley" and "Cold Mountain." His last screen appearance was in "Made of Honor," a romantic comedy currently in theaters, where he played the oft-married father of star Patrick Dempsey's character.
In recent years, Pollack also produced many independent films with filmmaker Anthony Minghella and a production company Mirage Enterprises.
The Lafayette, Ind. native was born to first-generation Russian-Americans. In high school, he fell in love with theater, a passion that prompted him forego college and move to New York and enroll in the Neighborhood Playhouse School of the Theater.
Studying under Sanford Meisner, Pollack spent several years cutting his teeth in various areas of theater, eventually becoming Meisner's assistant.
"We started together in New York and he always excelled at everything he set out to do, his friendships and his humanity as much as his talents," said Martin Landau, a longtime close friend and associate in Actor's Studio, through spokesman Dick Guttman.
After appearing in a handful of Broadway productions in the 1950s, Pollack turned his eye to directing - where he would ultimately leave his biggest mark. He helmed "The Way We Were" (1973), "Jeremiah Johnson" (1972), "Havana" (1990) and "The Interpreter" (2005).
"Sydney let the dialogue and the emotion of a scene speak for itself. Not given to cinematic tricks, his gentle and thoughtful touch and his focus on the story let us inhabit the world he created in each film," said Michael Apted, president of the Directors Guild of America.
But Pollack, who stood over six feet tall and had a striking presence on the screen, never totally gave up acting.
At the 2005 Tribeca Film Festival, Pollack said "Tootsie" star Dustin Hoffman pushed the director into playing the actor's exasperated agent. At that point, he hadn't acted in 20 years.
Pollack said Hoffman repeatedly sent him roses with a note reading, "Please be my agent. Love, Dorothy."
"Most of the great directors that I know of were not actors, so I can't tell you it's a requirement," he said. "On the other hand, it's an enormous help."
In the 1982 movie, Hoffman plays an out-of-work actor who pretends to be a woman to land a role on a soap opera.
"I didn't think anyone would believe him as a woman," Pollack said. "But the world did, they went crazy."
Pollack was survived by his wife, Claire; two daughters, Rebecca and Rachel; his brother Bernie; and six grandchildren.