Sinclair has been with rovers since he was 7 and was offered a professional contract at the end of his scholarship, but the chance to move to Chelsea's Academy was to much of a lure for him.
Sinclair told the Bristol Evening Post: "I want to thank Rovers who have been so good to me and understood that this was an opportunity I couldn't turn down.
"Chelsea's set-up is incredible and I didn't need much persuading to sign."
so far compenstation for Sinclair has not been discussed between the two clubs, but rumours are Bristol Rovers are hoping for a 7 figure sum, but it may well go to a Tribunal if no agreement it met.