The long, drawn out transfer saga is over and the Ghana midfielder is available to play against Arsenal on Sunday following is move from French champions Lyon.
Essien, 22, said: "I wanted to come to the Premiership and now I am very happy.
"I am in love with the Premiership. I am pleased to be with Chelsea.
"It is going to be tough but I am ready to fight for a place in the team.
"I don't think it will be a problem to adapt because I speak the langauge and I have some friends in the team.
"Physically I'm okay because I trained normally with my former club."