 On 16 May 2013, Sullivan signed a two-year deal with Portsmouth.He made his debut in a 4–1 home defeat to Oxford United on 3 August 2013.Sullivan went on a run of six matches as Portsmouth's first choice goalkeeper, however two high-profile errors against York City, one of which saw Sullivan drop the ball into an empty net, resulted in the arrival of Trevor Carson from Bury, and Sullivan was dropped from the side.