The 30-year-old winger has flitted in and out of Neil Lennon's starting XI since the former Hibs boss came in as interim Celtic manager following Brendan Rodgers' departure to Leicester.
Reports in the Scottish Sun earlier this month claimed the former Manchester City, Aston Villa and Swansea star could still leave during the close season, despite Celtic activating a clause in his contract tying him to the club until the summer of 2020.
Speaking to Celtic's YouTube channel ahead of this weekend's Scottish Cup final with Hearts, Sinclair insisted he wasn't on the move.
"I’ve always wanted to stay here - I think everyone knows my situation and how I love this club and want to be here.
"I love the fans and playing for Celtic. Games like this [the Scottish Cup final] and playing in cup finals – there’s nothing better.
"I was delighted [to sign a 12-month extension], I’m here for another year and I’m looking forward to it."
Sinclair has won eight trophies since joining Celtic under Brendan Rodgers for a reported £3.5 million in the summer of 2016. He has scored at least 17 goals for Celtic in each of his three campaigns, netting a total of 60 in all competitions from 153 appearances.