He is on the books of Drogheda United and wears shirt number 26. His main role on the pitch is Midfield. His stronger foot is Left. His estimated market valuation currently stands at 100K €.

His latest transfer saw him join Shamrock Rovers from Drogheda United via Loan on 2025-11-29.

Over 33 appearances in the Ireland Premier Division 2025, John O'Reilly-O'Sullivan contributed 0 goals and 0 assists, completed 7 key passes from 223 total passes, and posted a passing accuracy of 5.2.