The vote will take place between August 25-27 after a final debate, Renan Calheiros -- who is overseeing Rousseff's impeachment trial in the upper house -- told journalists in the capital Brasilia.
That will provide a few days' breathing space after the end of the August 5-21 Olympics, the first ever to be held in South America.
The Senate had originally considered August 16 for the impeachment vote before moving the date to August 22, which was also rejected as too close to the Games, amid fears that political tensions would ruin the atmosphere.
The leftist leader is accused of breaking budget laws by taking illegal loans to mask the country's true financial state.
She accuses her opponents of attempting to stage a right-wing coup d'etat, saying the accounting manoeuvres have long been common practice for Brazilian governments.
Her former vice president, center-right leader Michel Temer, has taken over as acting president. He has acted quickly to move the country away from Rousseff's leftist political platform, saying the sickly economy needs urgent reform.