The 21-year-old, who had temporary spells with fellow League Two sides Cambridge and Luton last term, will stay at Fratton Park until January.
He told the club website: “I’ve already got a lot of experience and hopefully I can contribute something to this good side.
“The size of the club and the style of play preferred by the manager both attracted me to the club.
“There’s a lot of talent around the place and I think we can all be optimistic about the season ahead.
“I’ve played at this level before and it’s a tough league to get out of, but there’s enough quality and character in this team to give it a good go.
“Pompey away was always a fixture you looked forward to and wanted to play in – now I’m happy to have the fantastic fans on my side.
“I’ve played here before when I was on loan at Torquay and we won. It’s a magnificent place to play football.”