The goalkeeper put pen to paper on the deal following the conclusion of the 2020-21 season to commit his future to the Reds following a watershed campaign, in which he made five first-team appearances and featured in both the Premier League and Champions League.
The 22-year-old also won his first cap for Republic of Ireland earlier this month, coming on as a second-half substitute against Hungary in Budapest.
Speaking about the new contract, Kelleher told Liverpoolfc.com: “I am happy to get it over the line and finally done; it was in the pipeline for a few months with negotiations and stuff, so I am delighted to get it done.
“For me, it was a positive moment to commit my future to the club for the next few years. It’s such a big club and it’s an honour to be a part of it, so when I got the chance to sign for a few more years I was obviously delighted. I just want to keep my progress going at the club, really.”
Watch our exclusive interview with Caoimhin Kelleher on his new deal
After tallying three League Cup outings and one in the FA Cup for Liverpool during 2019-20, Kelleher made his Champions League debut for the club on December 1 last year when he started against AFC Ajax at Anfield.
A maiden Premier League appearance followed versus Wolverhampton Wanderers five days later, with the custodian keeping clean sheets in both fixtures.
Although an injury kept Kelleher sidelined for a significant part of the final stages of the season, he ended the campaign with a total of five starts to his name.
“It was a big year for me in terms of playing the first-team games this year and more important games; being thrown into the Champions League and Premier League games was big for my development and being able to handle that,” he added.
“It gave me a lot of confidence to try to push on, to try to keep pushing Ali because I can play at that kind of level as well and do well. I am looking forward, try to keep pushing him and we’ll see what happens.”