Finnan signed a one-year contract with Premier League side Portsmouth on 31 July 2009. He made his debut for the club on 3 October in a 1–0 victory against Wolverhampton Wanderers at Molineux, and played regularly in the second half of the season, but with the club in administration and relegated to the Championship, he was not offered a new deal. His last appearance for the club was the 2010 FA Cup Final against Chelsea.