The August 13th to 23rd tournament in Cincinnati marks the 39-year-old's first appearance there since his 2023 title.
"I am very happy to announce that I will be in Cincinnati this year, for the first time since 2023," Djokovic said on the tournament's social media.
"That year I played one of the top three Masters 1000 finals of my career.
"I really look forward to coming back, playing in front of you again, and seeing all the fans from around the world. See you soon!"
The Serb, currently ranked fifth in the world, joins a dream line-up ahead of the US Open including Wimbledon winner Sinner, world number two Alexander Zverev and number three Carlos Alcaraz, who has been nursing a wrist injury since April.
After Cincinnati, Djokovic is expected at the August 30th to September 13th US Open, where he will bid for a 25th major title.