Serena and Venus Williams will play doubles in the WTA tournament in Cincinnati from August 13-23, the WTA writes on its website.
It will be the 44- and 46-year-olds' first match together since the 2022 US Open.
Serena Williams injured her knee during Wimbledon and the American sisters were forced to skip doubles at the Grand Slam tournament.
The last Grand Slam tournament of the year is the US Open, which is played from August 30 to September 13.
