He currently plays for Ross County, wearing the number 3 shirt. He plays primarily as a Defender. His current market value is estimated at 175K .

His most recent move was a from Glenavon Lurgan to Ross County on 2025-07-04.

Throughout the Scottish Championship 2025-2026, Len O'Sullivan featured in 26 matches, averaging 0 tackles, 0 interceptions, and 0 clearances per game, while blocking 0 shots per game.