Weintraub's first film as a Producer was Robert Altman's Nashville (1975). Until then, United Artists Producer David Picker had dismissed the script and would not make the film. A short time later, Weintraub was hosting a party for John Denver in New York, and among the guests he invited was Altman, whom he admired but had never met. "Altman pulled Weintraub aside," recalls the film's Screenwriter, Joan Tewkesbury, "and over a shared joint" Altman told Weintraub about the script. After another meeting with Altman, Weintraub was hooked on the story. However, no studio wanted to work with Altman, telling Weintraub that the Director was a "pain in the ass". Weintraub eventually managed to find Investors and gave Altman the $2 million he needed to make the film. Following Nashville , Weintraub's credits as Producer over the next few years included Oh, God! (1977), September 30, 1955 (1978), Cruising (1980), All Night Long (1981), and Diner (1982).

After several years at MCA, where he first started work as a mailroom clerk, he left and formed his own personal management company. While at MCA, he was assistant to Lew Wasserman, whom he thought of as a father figure. In the 1960s, he co-founded the vocal group The Doodletown Pipers. Among the acts that Weintraub managed at this time were Paul Anka, Shelley Berman, Pat Boone, Joey Bishop, The Four Seasons, Jackson Browne, Jimmy Buffett and singer Jane Morgan, whom he would later marry.

Weintraub's relationship with singer and Actress Jane Morgan went from professional to personal and the two were married in 1965. She was almost 41 years old, while he was 28. Because of her age, she was not able to have children and they ended up adopting three daughters. Weintraub also has a son from his first marriage. The couple separated in the 1980s, but never divorced. For 20 years until his death, Weintraub had been living with his girlfriend, Susie Ekins.

In 1970 Weintraub convinced Elvis Presley and his manager, Col. Tom Parker, to do his first national tour, something they had not considered, as Elvis was by then a successful film star. The tour, with a modern sound system created for it, helped develop Weintraub's career as a concert promoter.

He next promoted a tour for Frank Sinatra in 1974, whom Weintraub first put in Madison Square Garden's boxing arena. For the previous six years, Sinatra had basically retired due to the failure of his last album. Weintraub convinced him to do a tour, which led to Sinatra's "transformation from saloon singer to stadium singer," writes biographer Will Friedwald. "When Frank came out of retirement and started doing stadiums, he didn't know if he would draw," recalled Guitarist Al Viola. "Weintraub deserves most of the credit (after Sinatra, that is) for pulling this off," says Friedwald.

Following his years as a concert promoter, he began producing films. Among them were Director Robert Altman's Nashville (1975), Barry Levinson's Diner (1982), the original version of The Karate Kid (1984) and its 2010 remake, as well as the remake of Ocean's Eleven (2001), and its two sequels. Later, Weintraub was executive Producer of HBO's series The Brink and HBO's Behind the Candelabra in 2013, which won an Emmy. In 2014, he won another Emmy as co-producer of Years of Living Dangerously, a television documentary about global warming. In 2011, HBO broadcast a television documentary about Weintraub's life, called His Way.

Bob Dylan signed with Weintraub in 1978 after watching a Neil Diamond concert in Las Vegas, knowing that Weintraub managed the impressive event. He began a world tour beginning in Japan which continued through Europe and the U.S., in total performing 114 shows in front of two million people.

The success of The Karate Kid (1984), led Kirk Kerkorian, then owner of MGM/UA, to appoint Weintraub as chairman and CEO of the neglected United Artists division, with Weintraub acquiring a minority stake, but clashes between the two men led to Weintraub's departure after five months. The Karate Kid had several sequels, all produced by Weintraub, The Karate Kid Part II (1986), The Karate Kid Part III (1989) and The Next Karate Kid (1994).

In 1986, the National Association of Theater Owners named Weintraub the Producer of the Year. In 1991, he was named to the board of the Kennedy Center. Weintraub was one of the first independent film producers to be honored with a star on the Hollywood Walk of Fame. In 2007, a Golden Palm Star on the Palm Springs, California, Walk of Stars was dedicated to him.

Weintraub's later films as Producer were Happy New Year (1987), Pure Country (1992), The Specialist (1994), Vegas Vacation (1997), The Newton Boys (1998), The Avengers (1998), Soldier (1998), Nancy Drew (2007), The Karate Kid (2010), and the 2001 remake of Ocean's Eleven, for which he founded the company JW Productions. In addition to producing the sequels Ocean's Twelve (2004) and Ocean's Thirteen (2007), he appeared in all the Ocean's films. Weintraub had a small role in Vegas Vacation (1997) as "Gilly from Philly" a high roller casino gambler with two pals, and in The Firm (1993). He revived the acting career of Ellen Barkin who underwent a massive makeover for her role as Al Pacino's casino assistant.

Weintraub was a major contributor to many charities, including the Los Angeles County Museum of Art, the Museum of Contemporary Art, the Music Center, the UCLA School of Dentistry and the Children's Museum of Los Angeles. In 1988, the American Friends of the Hebrew University gave Weintraub and his wife, Jane, the Scopus Award in gratitude for their support. He was also a major supporter of Chabad and was close with the Lubavitcher Rebbe.

He also began doing charitable work to help stop the ongoing genocide taking place in Darfur in 2007. Weintraub, Matt Damon, George Clooney, Don Cheadle, and Brad Pitt cofounded the nonprofit organization, Not On Our Watch, dedicated to preventing mass killings in Darfur and other areas of the world. They also raised $9.3 million to aid their relief efforts.

He was executive Producer of HBO's series, The Brink, and HBO's Behind the Candelabra in 2013, an Emmy-winning drama about the last ten years in the life of Pianist, Liberace. In 2014 he also won an Emmy as co-producer of Years of Living Dangerously, a television documentary about global warming.

Weintraub died in Santa Barbara, California on July 6, 2015, at the age of 77. He was survived by his wife, Jane Morgan Weintraub, and his longtime companion Susan Ekins. He also was survived by a brother, four children and five grandchildren.

A television documentary film about Weintraub's life, called His Way, directed by Douglas McGrath, was broadcast on HBO in 2011. On a 2010 television appearance of The View, Weintraub made a handshake deal with Whoopi Goldberg to play the next God in a Future Oh, God! sequel, should a favorable script become available. Weintraub had agreed to produce a new adaptation of The Legend of Tarzan for Warner Bros. which was released on July 1, 2016.