The Irishman had been on loan with Reading FC since July, 2025.
During that time, the striker made 21 appearances for the League One outfit, scoring two goals.
However, a serious knee injury has stopped his season. He has now returned to Brighton for rehabilitation.
On March 22nd, the 21-year-old posted a message to reflect on the injury and his time at The Royals.
O’Mahony wrote: “Not the way I wanted this season to go or end, but always grateful for it and thanks to Reading FC for the time I had there.
“Time to recover and get ready for next season.”
In total, O’Mahony has made four senior appearances for Brighton and Hove Albion, including three in the Premier League and one in the EFL Cup.
His first start was under Roberto De Zerbi on April 28th, 2024, against Bournemouth.
Earlier that April, he was given a three-year contract extension by Albion.
In August 2024, He scored his first senior Brighton goal in the EFL Cup against Crawley Town.
The following day, Mark O’Mahony joined Portsmouth on a season-long loan from The Seagulls (August 28th, 2024).
He made 13 appearances for Pompey, scoring three.
He was then loaned straight to Reading for the 25/26 season.