The younger Bonaduce became famous as a child actor of the 1970s on the sitcom/television series The Partridge Family. Bonaduce co-starred as Danny Partridge, the wisecracking, redheaded middle son of the singing pop band (headed by Shirley Jones). He and Shirley Jones were the only Partridge cast members whose actual names were also that of the character he/she portrayed on screen. Danny was the fictional pop group's bass guitar player.

Bonaduce was part of The Adam Carolla Show in 2007. In 2008 he was given a daily one-hour solo spot known as Broadcasting Bonaduce, which was broadcast locally on the L.A.-based KLSX station. Broadcasting Bonaduce was removed from KLSX in February 2009, as the station had changed its format from talk to Top 40. On November 10, 2008, Bonaduce began hosting the morning drive time on WYSP in Philadelphia, where he remains today.

By his own account, Bonaduce grew up in a dysfunctional family and suffered physical and emotional abuse at the hands of his father.

The younger Bonaduce became famous at the age of ten in the television series The Partridge Family, starring as the middle son, Danny Partridge. Danny stood out with his naturally red hair and wisecracking that was a constant bane of the family's manager, Reuben Kincaid, portrayed by Dave Madden. In real life, Madden was something of a second father to Bonaduce, taking Danny into his home during periods of domestic strife in the boy’s own home. Bonaduce also had a close relationship with co-star Shirley Jones. However, following the end of the series, Bonaduce's late teens and twenties involved drug abuse and even a period of homelessness. On his own radio show on August 4, 1997, the actor related how he lived in his car behind Grauman's Chinese Theatre, while being greeted by fans and autograph seekers.

In 1985, Bonaduce married real estate agent Setsuko Hattori. They divorced in 1988. On November 4, 1990, Bonaduce met second wife Gretchen Hillmer on a blind date, and the two were married the same day. They had two children together, Isabella and Dante. By the time he met Hillmer, he had been fired by WEGX-FM in Philadelphia for drug use and had been arrested in Phoenix, Arizona for an altercation with a male transvestite. Bonaduce has publicly stated that Hillmer took an interest in him when no one else did, and that she went to great lengths to help him maintain his sobriety, which only lasted for brief periods. In an episode of A&E's Biography first telecast in 2006, Bonaduce openly discussed his long struggle with drugs and alcohol. On April 9, 2007, drug and alcohol abuse had taken its toll on the marriage, and Hillmer filed for divorce on grounds of irreconcilable differences.

Bonaduce is currently engaged to Amy Railsback; Railsback, who is 23 years his junior, was formerly a substitute school teacher and now manages Bonaduce's career full-time. They have been together since April 2007 and maintain homes in both Hollywood and Philadelphia.

In the television series The Partridge Family, the role of Danny Partridge was played by Bonaduce, a member of the musical Partridge family, a band and family that toured the country in their hip, Mondrian-inspired painted school bus. The bass guitar was played by Danny Partridge. The backbone of the band's sound was provided by the rhythm section led by Danny and also including percussionist siblings Tracy and Chris.

Bonaduce's eponymous debut LP was released in 1973 by Lion Records, a subsidiary label of MGM Records. Bonaduce has admitted that his vocals can barely be heard on the album; most of the singing was provided by Bruce Roberts.

Bonaduce made several movies during and after the run of The Partridge Family. Perhaps the most memorable of his films was Corvette Summer (released in 1978), starring Mark Hamill (of Star Wars fame.) Hamill and Bonaduce played high school students who went in search of a stolen customized Corvette Stingray. Bonaduce also made guest appearances on several TV shows, including multiple appearances on the popular police dramedy CHiPs. His career withered in the early 1980s.

A cameo appearance was made by Bonaduce in a 1994 episode of Married... with Children along with Partridge Family costar Dave Madden. That same year, he appeared on an episode of Space Ghost Coast to Coast; he has also guest-starred on CSI: Crime Scene Investigation, Season 7 Episodes 1 and 2 and the fourth season of The Drew Carey Show as the son of Shirley Jones' character.. Bonaduce has appeared as himself on the detective series Monk, and on the show Girlfriends. Bonaduce guest-starred with J. D. Roth (who he would later reunite with for Breaking Bonaduce) on an episode of Sex Wars. In 1999, Bonaduce appeared in the Christmas episode, "Sabrina, Nipping at Your Nose", of Sabrina, the Teenage Witch, after Salem buys a Twelve Days of Christmas package at the 89 Cents Store, Bonaduce appears sitting in a pear tree, which Salem then exclaims, "Danny Bonaduce! This is the best "Partridge" in a pear tree I could ask for!".