The Belgium international agreed a 12-month contract extension with Chelsea on Friday (AEST), meaning he is under contract until 2022, before finalising a season-long switch to Selhurst Park.
Batshuayi scored six goals in 13 appearances for Roy Hodgson's side during his previous spell in south London in the second half of the 2018-2019 campaign.
And the 26-year-old, who has struggled to hold down a place in Chelsea's first team since joining in 2016, is hoping to have a similar impact at Palace this coming season.
"I had a lot of other clubs [interested] but my head is here, so everything is right and happy now," he told Palace's official website.
"I'm happy, the coach is happy, the team-mates are happy. So, let's get to work.