The Blues lead the Premier League in clean sheets and fewest goals conceded.
Cahill has admitted that the rotation system that was in place at Stamford Bridge before this season made it difficult for him and Terry to strike up a relationship, and believes that manager Jose Mourinho making them his undisputed first-choice centre-backs has helped them become more "comfortable" as a unit.
"Yes, we are comfortable next to each other," he told The Mirror. "You can see the partnership works well. Since I have been at Chelsea it has been difficult for us to get together and stay together consistently.
"Early on, when I first came here, we were in a rotation where we played three then missed one. Last year, John had a few injuries, which he has not had before. So to get him back this season has been fantastic for us.
"His performance level has been top drawer again and, for me, to play alongside him consistently has been great. We had a playing relationship before I came to Chelsea with England and if you look back at those games, we kept a few clean sheets so it was working well."
Former England captain Terry has rebuffed speculation that he could come out of international retirement to partner Cahill for the Three Lions at the World Cup in Brazil this summer.