The Blues entered the October international break with a five-point lead at the top of the standings after dropping just two points in the opening seven games, in a draw at defending champions Manchester City, who are second.
Striker Diego Costa, with nine goals in seven Premier League games, and playmaker Cesc Fabregas have slotted seamlessly into Mourinho's side, leaving many to wonder who can beat Chelsea to a first title since 2010 this season.
Ivanovic believes Chelsea will improve as the players get to know each other better.
"It is really amazing how quickly the new players have adapted," the Serbia defender said in the Chelsea magazine.
"You could see straight from the first day how they work, how well they do their jobs, and that it is normal for them to play this way.
"That is why they are here and we are all very happy about that.
"As this group stays together for a long time, we will get better and better - we know each other's games, we know the movement of each other and this gives us the opportunity to play more easily in games."
Mourinho has pointed to his team's potential to improve and also to their adaptability regarding tactics, including at City, where Chelsea shut down their opponents and almost stole a victory but for their former midfielder Frank Lampard, who netted a late equaliser.
Ivanovic believes understanding one another is even more key than specific tactical work.
Ivanovic added: "Sometimes we work on special things in preparation for a game, and this is one thing, but it is another to understand your team-mates, to know how they work and what they like on the pitch.
"The moment you start to see what they usually do in training, you know they will usually do this in the game
You have to feel that."
Source : PA