The England defender made the move from Bolton on Monday and immediately set his sights on testing himself against Europe's best.
"That's the whole reason you want to move," he told Chelsea TV. "You want to play at the top level and the Champions League is the top level.
"I've only played in Europe when I first moved to Bolton; (Atletico) Madrid away, Sporting Lisbon, teams like that.
"It'll be a new experience for myself, and I'm looking forward to pitting my wits against the top players in the world."
Cahill's new captain and central defensive partner, John Terry, is also delighted the 26-year-old will be available to boost the Blues' European campaign ahead of their last-16 clash with Napoli.
"He's a great addition and he hasn't played Champions League football, which is an added bonus for us," Terry said.
"He's a great defender; he reads the game well, he's got a bit of pace and he's good in the air - he scores important goals, he has done for Bolton.
"I'm looking forward to playing alongside him, it's really good to have him on board so early."
Cahill's move took some time to be resolved amid wrangling over personal terms with his new club.
But he had only kind words for his former employers as he prepared for life after Bolton.
"I've got nothing but praise for the club, from Phil Gartside all the way down," he said. "They gave me the platform to be where I am today.
"I'd got to the stage at Bolton where it was nice to move on - some move on with sour grapes but I've moved on great terms, for a forward step in my career.
"I need to keep moving upwards, hopefully I've got my best years ahead of me.
"I can improve on a lot of things, at the top level it's more the concentration levels than anything else because there can be long spells where you've got a lot of the ball, which I'm not used to.
"It's also the experience of playing the top games, it's where I've always wanted to be in my career.
"It's difficult to move in mid-season but I'm looking forward to puling on shirt. I want to get in the team first and foremost and hopefully become a fixture."