The 29-year-old has signed a four-year deal with Pompey and will cost the club around £1.8million.
“I spoke to Paul Hart and it sounded brilliant,” he told Pompey’s official website.
“Everything down here is certainly what I was looking for and I’m sure I’ve made the right decision.
“The supporters here are well renowned for being fantastic, loyal and very, very noisy. When I’ve played here the atmosphere’s been electric and it’ll be nice to be on the right side of them this time.”
