Midfielder Bakayoko signed a five year deal at Stamford Bridge following his £40m switch from Monaco on Saturday.
The 22-year-old helped Les Rouges et Blancs to win Ligue 1 and the semi-finals of the Champions League last season.
Bakayoko would beef up Conte’s midfield stocks, though his debut may have to wait until September after knee surgery in the off-season, which held up the move somewhat.
Bakayoko said: “I am very happy to be here and to join this great team. I have grown up watching Chelsea. Signing was the natural thing for me because it is a club I loved very much in my childhood.
“I am now looking forward to evolving under this fantastic coach and alongside so many great team-mates.”
But hours after completing the move he was sitting watching the Blues cruise to an 8-2 demolition of the Cottagers.
Antonio Conte picked an almost first-choice XI for the behind closed doors friendly at the Cobham training ground.
Brazilian winger Willian scored a first half hat-trick, with Michy Batshuayi bagging a brace to hand the Blues a 5-0 lead at the break.
Wantaway striker Loic Remy scored twice before Cesar Azpilicueta completed the rout from the spot.