Updated September 5, 2026 · 5 min read · by Jake Hari
Who won the 2026 US Open mixed doubles? Karolina Muchova and Jakub Mensik, who beat Belinda Bencic and Flavio Cobolli 6-3, 1-6, [10-6] in the final on Wednesday, August 26, 2026, to split the $1 million prize. Serena Williams and Carlos Alcaraz won their opener and lost in the quarterfinals to Bencic and Cobolli.
Kalshi never listed a mixed doubles market, and no public sportsbook posted one either. The only price that carried this event sat on the men's singles board, where Alcaraz's title contract slid from 33 cents on Monday, August 24, to 26 by Thursday morning. The full results and that board, as it stood on August 27, are below.
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Who Took The $1 Million
Seeds in parentheses:
| Round | Winners | Beat | Score |
|---|---|---|---|
| Final | Muchova / Mensik | Bencic / Cobolli (4) | 6-3, 1-6, [10-6] |
| Semifinal | Muchova / Mensik | Andreeva / Rublev | 5-4(6), 3-5, [11-9] |
| Semifinal | Bencic / Cobolli (4) | Svitolina / Monfils | 4-5(7), 4-1, [10-5] |
| Quarterfinal | Bencic / Cobolli (4) | Williams / Alcaraz | 5-4(4), 4-1 |
| Round 1 | Williams / Alcaraz | Routliffe / Glasspool | 5-3, 4-1 |
| Round 1 | Bencic / Cobolli (4) | Townsend / Zverev | 4-2, 4-2 |
| Round 1 | Siniakova / Patten | Sabalenka / Djokovic (1) | 1-4, 4-2, [10-2] |
| Round 1 | Shnaider / Ruud | Pegula / Fritz (2) | 4-2, 4-1 |
| Round 1 | Andreeva / Rublev | Errani / Vavassori | 1-4, 4-1, [11-9] |
Both semifinals went to match tiebreaks, and the champions were two points from losing theirs. Muchova and Mensik, an all-Czech pairing, saved two match points against Andreeva and Rublev, trailing 8-5 in the match tiebreak before Mensik saved one with an ace and closed it with an unreturnable serve two points later. Bencic and Cobolli came through the other half against the married pairing of Elina Svitolina and Gael Monfils, dropping their first set of the event and then winning four straight games to force the tiebreak they dominated.
The final, the only match of the event played to full six-game sets, came down to a match tiebreak too. Mensik's ace on set point took the opener in under half an hour, Bencic and Cobolli ran away with the second, and the Czechs pulled ahead 8-4 in the decider on Mensik's serving and net play. It was their first Grand Slam trophy as a team, won against a pairing that had arrived at the final a perfect 7-0 together. "I wasn't really expecting to be standing here tonight," Muchova said, which was roughly the market's position on everyone left standing by Wednesday.
Where The Seeds Went
Tuesday's opening session cleared the marquee names in a single day of short sets. Top seeds Aryna Sabalenka and Novak Djokovic lost their opener to Katerina Siniakova and Henry Patten, the world's top-ranked doubles players. Second seeds Jessica Pegula and Taylor Fritz fell to Diana Shnaider and Casper Ruud. Two-time defending champions Sara Errani and Andrea Vavassori held match points and still lost to Mirra Andreeva and Andrey Rublev.
Sets to four games with no-ad scoring compress the talent gap until one swing decides a set, and in that shape nobody's name is worth its seeding. The doubles specialists' edge lasted one round: all four semifinal teams were built from singles players.
How Far Serena And Alcaraz Got
Williams and Alcaraz beat Erin Routliffe and Lloyd Glasspool, a top-shelf doubles pairing, in their opener, and the details mattered more than the score. Williams, 44, was playing her first US Open match since 2022. She hit a 120mph ace that drew gasps out of Arthur Ashe, and Alcaraz worked through visible early rust in his first competitive tennis since April. "I never expected to be back on this court," Williams said afterward. "I never thought this would happen."
The quarterfinal was the ceiling. Bencic and Cobolli beat them in 55 minutes and played the second set without an unforced error while the wild cards leaked early mistakes. "We felt their aura for sure. It was an honor to play," Bencic said. Cobolli, who had called the pairing "the queen of tennis and the king of now" before the match, put it more simply: "Playing Serena and Carlos on Arthur Ashe is not easy. So now, maybe we take a beer."
What Kalshi Priced While It Happened
This is the top of Kalshi's men's singles winner board as pulled Thursday morning, August 27, three days after this page's original Monday table. Prices are cents per contract that pays $1 if that player wins the title; here is how Kalshi's cent prices work.
| Player | Last Trade | Bid | Ask |
|---|---|---|---|
| Carlos Alcaraz | 26¢ | 25¢ | 26¢ |
| Alexander Zverev | 20¢ | 19¢ | 20¢ |
| Novak Djokovic | 11¢ | 9¢ | 11¢ |
| Ben Shelton | 8¢ | 7¢ | 8¢ |
| Arthur Fils | 8¢ | 7¢ | 8¢ |
| Rafael Jodar | 6¢ | 5¢ | 6¢ |
| Taylor Fritz | 5¢ | 4¢ | 5¢ |
The full board ran 35 names; this was its liquid top.
Alcaraz went from 33 cents to 26 in a window where he won a match, played competently, and had no reported injury. Zverev did not move, so the favorite's cushion over the second choice shrank from 13 cents to six.
The women's board barely reacted: Sabalenka stayed on top at 22 cents, with Iga Swiatek and Coco Gauff at 15 behind her. The defending champion's Tuesday doubles exit cost her singles price nothing, so the market treated her loss as noise and Alcaraz's week as signal.
Why Alcaraz's Price Fell
The market did not wait for the tennis. The contract moved lower on Monday before he hit a ball, again through his two Tuesday matches, and once more on Wednesday, where it held at 26 through Thursday.
The matches themselves settled nothing. He shook off the rust, moved well, and won the match his team was supposed to win, but observers thought he looked slightly off the pace on serve. Serve speed was the tell this page flagged before the event, because a wrist that will not snap through contact shows up there first. Then came the detail the market chewed on Wednesday: Alcaraz cancelled his scheduled practice on Arthur Ashe the day after his exit, the slot went to Sabalenka and Zeynep Sonmez, and he was not expected back on a practice court until Thursday. No wrist problem was reported, but a favorite carrying a quarter of the board does not get the benefit of the doubt in a week when the only new information is a skipped practice.
The direction fits the models. When our eight-model panel priced this board blind, every seat put Alcaraz below the market, with a median of 16.4% against what was then a 33-cent quote. Two mixed doubles matches were the one piece of evidence that could have closed that argument in the market's favor, and instead the price moved toward the models. At 26 cents it had covered about half the distance and still sat ten points above the panel's median, which meant the market believed in the wrist considerably more than the models did. One of them had to be wrong by September's second Sunday.
Bottom Line
The $1 million was settled on the court, and the most famous team in tennis got two matches and a farewell worth the ticket. The price that carried the week was Alcaraz's. As of August 27, the defending champion carried 26 cents into a singles main draw that began Sunday, August 30, and that number has not been re-pulled since. If our tennis experts take a side as the draw plays out, those reads land on our free expert picks board. For how Kalshi's board stacks against Polymarket and the sportsbooks on this field, our US Open odds comparison carries that map. Hero illustration: OddsShopper, in the house collage style. Serena Williams photo by Katherine Shann, licensed CC BY-SA 2.0; Carlos Alcaraz photo by Barcex, licensed CC BY-SA 4.0; photos cropped, toned, and composited.
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