Sinclair seals move to Manchester City
The club did not disclose any contract details for the 23-year-old winger, who was a member of the Great Britain team at the London Olympics.
"I'm just glad everything is settled and that I'm now a City player," Sinclair told City's website.
"There were times when I thought it might not happen so I'm relieved that I'm here and I can't wait to get started."
Sinclair could be included in the Manchester City squad for Saturday's home game against Queens Park Rangers.