Caoimhín Kelleher began his youth career at Ringmahon Rangers in his native County Cork, Ireland. In 2015, he joined the Liverpool Academy, and first featured for Liverpool’s first team during the pre‑season tour of the United States in 2018. In August 2018, he signed a new long‑term deal at the club.

Kelleher was an unused substitute in the Champions League Final victory over Spurs in 2019, becoming the first Irish player in over a decade to be included in the matchday squad of a Champions League–winning team. Kelleher required wrist surgery before the 2019–20 season; however, he still made the bench as Liverpool beat Chelsea to the UEFA Super Cup while Alisson was injured.

Kelleher made his competitive debut in September 2019, keeping a clean sheet in an EFL Cup win against MK Dons. In December 2020, he made his first Champions League start—again keeping a clean sheet in a win over Ajax.

Just five days later, he made his Premier League debut and recorded a 4 – 0 clean sheet victory over Wolves. Those performances cemented his status as Alisson’s second‑choice keeper.

In 2021, Kelleher signed another long‑term contract and, in February, won his first winners’ medal by scoring the decisive spot‑kick in the EFL Cup Final shootout against Chelsea.

Over the next few seasons, he earned a reputation as a penalty‑shootout specialist, helping Liverpool prevail in four separate shootouts, including another EFL Cup triumph over Chelsea in 2024.

Widely regarded as one of the best second‑choice keepers in world football, Kelleher now faces stiff competition following the arrival of Giorgi Mamardashvili this summer.

It seems likely he will depart to seek regular first‑team football—with the blessing of Liverpool supporters—after stepping up during Alisson’s injuries and contributing ten appearances to Liverpool’s 2024–25 Premier League title win.