Ivanovic joined Chelsea over six years ago from Lokomotiv Moscow and the Serbia international has made over 250 appearances for the club.
He has recently been linked with a summer move to Paris St Germain, but the 30-year-old is enjoying his time under Jose Mourinho.
The Blues currently lead the table by four points and Ivanovic is delighted with the potential that lies within Mourinho's squad.
"I can say this is the happiest I have been at Chelsea because, at the moment, the team is doing well and things are going right for us," said Ivanovic ahead of Serbia's friendly with the Republic of Ireland on Wednesday.
"We have improved as a team since the beginning of the season, it looks like we are a very strong team but we have the potential to make and build an amazing team."
Ivanovic's international team-mate Aleksandar Kolarov is a rival on the domestic front, with the latter's Manchester City side trying to hunt down Chelsea.
City are six points adrift of Chelsea, but have two games in hand and a superior goal difference, although Ivanovic and Kolarov have not been discussing the title battle.
"We are here together to help our national team and that is what we are focused on," added Ivanovic. "We don't talk a lot about the league.
"I think it will be very tough, both teams are fighting hard for the title and both have the quality to win it.
"It will be very interesting. We are both trying very hard to stay on top of our games and help our clubs."