Don Friedman was born May 4, 1935, in San Francisco, the son of an immigrant father from Lithuania and an immigrant mother from Germany. He began classical piano at four, then switched his attention to jazz at fifteen after his family relocated to Los Angeles, drawn first to Bud Powell's playing. He studied composition briefly at Los Angeles City College and spent his later teens and early twenties working the Los Angeles jazz scene, where he performed with Dexter Gordon, Chet Baker, Buddy DeFranco, and, before Ornette Coleman's arrival in New York made him famous, Ornette Coleman himself; he was also, for a time, a member of trumpeter Clark Terry's big band, the start of an association with Terry that would resurface on record for the next four decades.

Friedman moved permanently to New York in 1958. For roughly a year he shared a Manhattan apartment with a young bassist named Scott LaFaro, not yet the future star of the Bill Evans Trio. The two recorded together in a 1961 studio session with drummer Pete La Roca that went unreleased for decades, eventually surfacing on Resonance Records' 2009 LaFaro compilation Pieces of Jade. LaFaro was killed in a car accident that July, months after the session. That same year, producer Orrin Keepnews signed Friedman to Riverside Records, and Friedman also made two of the most significant sideman appearances of his career: Eric Dolphy, Ron Carter, Max Roach, and trombonist Julian Priester joined trumpeter Booker Little and Friedman on Little's Out Front (Candid, recorded October 1961), a hard-bop date that pushed toward the era's emerging avant-garde. Little died of uremia the following March at twenty-three; his last studio recording, issued the following year as Booker Little and Friend (Bethlehem), again used Friedman on piano alongside George Coleman, Priester, Reggie Workman, and Pete La Roca.

Friedman's own Riverside albums followed in quick succession: A Day in the City: Six Variations on a Theme (1961, with bassist Chuck Israels and drummer Joe Hunt), Circle Waltz (recorded May 14, 1962, the same trio with Pete La Roca replacing Hunt on drums), Flashback (1963, with Dick Kniss and Dick Berk), and Dreams and Explorations (1965, a quartet adding guitarist Attila Zoller). Down Beat's 1964 International Critics Poll named Friedman a "Talent Deserving Wider Recognition" pianist, the same year Zoller won the equivalent guitar category, and the two continued to record together on and off for more than thirty years. Friedman's next studio album, Metamorphosis (1966, Prestige), reunited him with Zoller alongside bassist Richard Davis and drummer Joe Chambers, engineered by Rudy Van Gelder.

Through the 1970s and 1980s Friedman worked steadily as a New York freelance pianist and teacher rather than a headliner, recording occasionally for European and Japanese labels: Themes and Variations (1979, Germany), Avenue of the Americas (1980, France), and the co-billed Hot Knepper and Pepper (1980), a session with trombonist Jimmy Knepper and baritone saxophonist Pepper Adams, plus bassist George Mraz and drummer Billy Hart. The Clark Terry association from his Los Angeles years resumed on record with Terry's It's What's Happenin' (Impulse!, 1967) and continued intermittently for decades, through Friendship (2002, Columbia), a session co-billed to Terry and Max Roach. Friedman also became a favorite in Japan, recording extensively for Japanese labels including two 1994 duo dates with altoist Lee Konitz: Lee Konitz Meets Don Friedman and, two years later, the three-way Thingin (hat ART, 1996), which brought Zoller back into the studio with both men. His 1994 solo recital At Maybeck was recorded for Concord's Maybeck Recital Hall Series.

Friedman kept recording into his eighties. Don Friedman Plays Don Friedman and a duo album with pianist Hank Jones, Alone Together, both appeared in 2012 on the German label Edition Longplay. In 2013 he was the pianist on saxophonist Shauli Einav's Generations (Posi-Tone), a quintet session that also carried bassist Or Bareket, a young Israeli musician then several decades his junior (see Related Artists). Bassist Phil Palombi led Re: Person I Knew: A Tribute to Scott LaFaro (2011), bringing Friedman back to the music of his late roommate, and in 2016 Friedman's own quartet, featuring guitarist Peter Bernstein, recorded Remembering Attila Zoller, honoring the guitarist he had first recorded with half a century earlier. His final album, Strength and Sanity (Newvelle Records, produced by his former student Elan Mehler), found his trio revisiting compositions from Out Front and Booker Little and Friend, the two Booker Little sessions that had helped launch his New York career fifty-five years before. Don Friedman died of pancreatic cancer on June 30, 2016, at his home in the Bronx, survived by his daughter, the actress and writer Lynn Adrianna Friedman.

Friedman's playing was built on a classical technical foundation and a bebop vocabulary rooted in Bud Powell, but critics from Leonard Feather to AllMusic's Scott Yanow consistently reached for Bill Evans as the nearest comparison, pointing to his harmonically dense chord voicings and the close listening he brought to trio interplay; Friedman himself drew as much on the phrasing of John Coltrane, Sonny Rollins, and Charlie Parker as on any pianist. The New York Times described him, on his death, as a "versatile pianist who moved easily between the modern-jazz mainstream and the more volatile jazz avant-garde," a range borne out by a catalog that runs from the hard-bop trio dates of his Riverside years to the freer, more open-textured guitar-and-piano dialogues he sustained across three decades with Attila Zoller. That Zoller partnership, along with a long-running association with Clark Terry that spanned from his pre-fame Los Angeles years to a 2002 studio reunion, and later duo and trio recordings with Lee Konitz, mark Friedman as a musician defined as much by a handful of deep, decades-spanning collaborations as by any single working band.