The news was confirmed by a post on Becker's personal website. No cause of death was announced.
The more retiring full-term member of the group, Becker was partnered with singer-keyboardist and co-writer Donald Fagen on a string of jazzy, sleekly produced singles and albums that ruled the charts during the '70s. After a protracted hiatus, "the Dan" returned to popularity in the '90s; their 2000 album "Two Against Nature" collected four Grammys, including one for album of the year.
The pair's gimlet-eyed, covertly perverse music, garbed in gleaming pop melodies, bebop-derived harmonies and shimmering production, was variously performed with a core working band in the group's initial heyday; those players were ultimately, and permanently, supplanted by a rotating cast of mostly jazz-schooled studio sidemen.
Becker was largely absent from the musical stage during Steely Dan's extended separation from 1981-93. It was only after the group's reunion that he undertook solo recording: His albums "11 Tracks of Whack" (produced by Fagen in 1994) and "Circus Money" (2008) failed to duplicate the band's success.
He was inducted into the Rock and Roll Hall of Fame with Fagen in 2001; with typical dry humor, the pair tersely solicited questions from the star-filled audience during one of the shortest acceptance speeches on record.
Becker was born Feb. 20, 1950 in Queens, N.Y., and was raised in the borough community. Initially a saxophonist, he took up the guitar as a teen.
He encountered his future partner Fagen as a student at Bard College in Annandale-on-Hudson, NY, while playing a gig at the local club the Red Balloon. In his 2013 memoir "Eminent Hipsters," Fagen - who studied music and English at the school -- recalled, "His amp was tweaked to produce a fat, mellow sound, and turned up loud enough to generate a healthy Albert King-like sustain."
The musicians bonded over their love of jazz and blues and the writing of such novelists as Vladimir Nabokov and humorists Bruce Jay Friedman and Terry Southern. They performed together in a number of campus bands, including one, the Leather Canary, which included classmate and future "Saturday Night Live" star Chevy Chase on drums.
Becker withdrew from Bard without a diploma; after Fagen graduated in 1969, the musicians moved to Brooklyn to find work in the professional music business. They served as studio members of the pop act Jay and the Americans. In 1971, the duo decamped to Los Angeles to serve as house songwriters for ABC/Dunhill, the publishing firm operated by the Americans' record label.
Impressed by Fagen and Becker's songwriting, label president Jay Lasker offered the pair a contract with the label. They organized a working group with New York guitarist Denny Dias, guitarist Jeff "Skunk" Baxter and drummer Jimmy Hodder; on early recordings with this lineup, Becker usually served as bassist.
Dubbed Steely Dan after a like-named sex toy in William S. Burroughs' black-hearted novel "Naked Lunch," the unit debuted in 1972 with the LP "Can't Buy a Thrill." Produced by Gary Katz (who shepherded all the act's '70s releases), it spawned the massive radio hit "Do It Again," which climbed to No. 6; the follow-up single "Reeling in the Years" peaked at No. 11.
The sophomore set "Countdown to Ecstasy" (1973) - which included "My Old School," a backhanded tribute to Fagen and Becker's alma mater Bard - was perhaps too bitter for most listeners and failed to produce any hits.
However, album rockers lofted the 1974 collection "Pretzel Logic" to No. 8. Driven mainly by the work of such jazz-bred sidemen as saxophonists Jerome Richardson and Ernie Watts and bassist Wilton Felder of the Crusaders, the album included the No. 4 single "Rikki Don't Lose That Number," which baldly lifted the keyboard hook of jazz keyboardist Horace Silver's "Song For My Father."
Growing tension within the band and Fagen and Becker's antipathy for touring led to the dissolution of the touring Steely Dan configuration in 1974, and the duo would thereafter perform with a succession of studio musicians. Becker increasingly took on lead guitar chores, though such players as Lee Ritenour, Rick Derringer, Dean Parks, Elliott Randall, Larry Carlton and Mark Knopfler also contributed.
The albums "Katy Lied" (No. 13, 1975) and "The Royal Scam" (No. 15, 1976) bore no hit singles, but were lofted by FM radio play. The group's biggest early hit came with "Aja," a shimmering No. 3 set that included the top-20 singles "Peg" and "Deacon Blues."
A confluence of difficulties led to the band's 1981 dissolution. The prolonged making of "Gaucho," which contained Steely Dan's final top-10 hit "Hey Nineteen," witnessed burgeoning antipathy between the two long-running partners.
"It was the 'Gaucho' album that finished us off,' Becker said in a 1994 interview with England's Independent. "We had pursued an idea beyond the point where it was practical. That album took about two years, and we were working on it all of that time - all these endless tracking sessions involving different musicians. It took forever and it was a very painful process."
The personality clashes were exacerbated by a lawsuit engendered by the drug overdose death of Fagen's girlfriend Karen Stanley and a serious injury sustained by Becker when he was struck by a New York cab.
Becker retreated to the Hawaiian island of Maui, where he grappled with drug abuse and laid low. "I spent a couple of years not doing any music or anything, just here in Hawaii trying to get healthy and adjust to the new regimen I was setting up for myself," he told England's Mojo magazine in 1995.
He crept back to work as a producer, helming albums by China Crisis ("Flaunt the Imperfection," 1985), Rickie Lee Jones ("Flying Cowboys," 1989) and Michael Franks ("Blue Pacific," 1990).
His work on Rosie Vela's 1986 collection "Zazu" marked his first work with Fagen since the breakup of Steely Dan; five years later, he gigged informally with Fagen's group the New York Rock and Soul Revue, which harbingered the partnership's touring reunion in 1993 in support of the comprehensive boxed set "Citizen Steely Dan."
An extended period of studio work resulted in the self-produced "Two Against Nature," which climbed to No. 6 and collected new kudos. The following year, Bard dropout Becker and partner Fagen received honorary music doctorates from the Berklee College of Music.
A second new Steely Dan release, the No. 9 set "Everything Must Go" (2003), included Becker's first-ever lead vocal with the group, on the track "Slang of Ages."
In later years, Becker also served as a writer for the jazzy vocalist Madeleine Peyroux's "Half the Perfect World" (2006) and "Bare Bones" (2009).