Pompey have reached a mutual agreement with Havant & Waterlooville to sign Nigel Atangana.
The 25-year-old midfielder has penned a two-year deal at Fratton Park.
Blues boss Andy Awford said: “I watched Nigel play on numerous occasions for the Hawks last season and was impressed with what I saw.
“I believe he’s capable of making the step up and playing in the Football League.
“I’d like to thank Derek Pope and Lee Bradbury at Havant & Waterlooville for their assistance and support because there was interest from other clubs.
“But it’s great that Nigel’s chosen to come and play for Pompey and I look forward to working with him.”
Hawks director Trevor Brock added: “Pompey have got themselves a special player. He’s been fantastic for us and I’m confident he’ll be a success at Fratton Park.
“I’m very pleased that we’ve been able to negotiate a deal with Pompey in preference over several other interested clubs.”
Atangana signed for the Hawks last summer and previously played in his homeland for Dives and Gravelines.