The eighth seed will face top seed Alexander Zverev on Sunday for the title. No American man has won a Grand Slam singles crown since Andy Roddick at Flushing Meadows in 2003.
Shelton, 23, is the youngest American US Open men’s finalist since Roddick, then 21, in 2003. He is also the first US man to reach the final here since Taylor Fritz in 2024.
“I am going to need you guys on Sunday,” Shelton told the Arthur Ashe Stadium crowd. “I'm going for it here. I'm going to leave it all on the court. I hope you guys come back me. Let's do this for the USA.”
Tiafoe took the opening set after Shelton double-faulted at 4-4. The eighth seed then found his range, breaking to lead 5-3 in the second set and closing it with a 132mph first serve. In the third, he won a 28-ball rally at 2-2 and later broke again in a 15-minute game featuring seven deuces.
Shelton sealed victory by breaking at 6-5 in the fourth. He finished with 47 winners and 20 aces in three hours and 17 minutes.
The win improved Shelton’s head-to-head record against Tiafoe to 4-1. He had already beaten defending champion Carlos Alcaraz in a five-set quarter-final that ended at 3:33am, the latest finish in US Open history.
Shelton is 4-0 in tour finals this season after titles in Dallas, Munich, Stuttgart and Montreal. Zverev leads their head-to-head 5-0, but the American will have home support after also upsetting Alcaraz.
Tiafoe, 28, rises four places to No. 8 in the live rankings. Shelton described him as “like a big brother” and said sharing Arthur Ashe Stadium with him was “super special”.
Sunday’s final offers a record $5.5 million to the champion. Shelton will attempt to end America’s 23-year wait for a men’s major singles title.