Williams, in her first competitive match in Arthur Ashe Stadium since her 2022 retirement, paired with Spain's Alcaraz, himself back after a lengthy injury layoff, to advance to the quarter-finals in straight sets.
Williams, a six-time US Open singles champion, and Alcaraz, a two-time winner and defending men's singles champion, defeated the British-New Zealand pair of Lloyd Glasspool and Erin Routliffe 5-3, 4-1.
The match began inauspiciously for the high-wattage pairing, with Alcaraz double-faulting and losing serve.
But the dream team turned the tide midway through the opening set of the shortened-format competition, breaking back to get back to level and then a second time in the opening set's final game.
At 30-30, Williams let out a trademark roar as she rifled a forehand return of serve winner cross court and out of reach. Alcaraz matched her on the next point, sealing the set with a big forehand passing shot up the line.
Afterwards, Alcaraz acknowledged feeling "really, really nervous" at the outset, noting he had been out for more than four months, but Williams "made it really easy," said the Spaniard, who also saluted the crowd.
The pair will next play the pair of Belinda Bencic of Switzerland and Flavio Cobolli of Italy.
US Open 2026
The US Open is the fourth and final Grand Slam of the tennis season, running from August 30th to September 13th. It is a hard-court tournament held at Flushing Meadows in New York City. Follow the links below for more information!
All you need to know | Men's qualifying | Women's qualifying | Latest US Open news