In early January 2005, after having been frozen out by Claudio Ranieri, Pellegrino joined former Valencia boss Rafael Benítez at Liverpool on a free transfer, signing a six-month contract– this move made him the first Argentine player in the history of the club. He played 12 times for the "Reds" in the Premier League – 13 overall – but his performances were not enough to secure a longer contract, and he was released by the club at the end of the season. He was cup-tied for the Champions League campaign, and did not feature in the victory over A.C. Milan in the final of the competition.