The 22-year-old subsequently watched Chelsea run riot in an 8-2 friendly win over Fulham at their Cobham training ground and he thanked Batshuayi - who scored twice in the rout - for his impact on the transfer.
Bakayoko and Batshuayi had swapped a series of emoji-laden tweets late on Thursday, hinting that the deal could soon go through.
"Thanks to my agent @mbatshuayi," Bakayoko wrote on Twitter alongside a brief statement.
"I would like to say thank you to all my fans and followers for your kind words throughout this journey - as you know, I love championships!
"As a Ligue 1 champion, I am even more determined to win as many championships as I can with my dream team Chelsea. I am pleased to represent the Blues!
"Thank you, yours truly, TB."