The 21-year-old right-back came through the academy ranks at Pompey and has already made 18 senior appearances for the side.
Mnoga joined National League side Aldershot on loan in January and featured 16 times, picking up seven cautions.
His performances with Aldershot attracted interest from League Two outfits Newport County and Walsall and Aldershot were keen to bring him back for another season.
Portsmouth boss John Mousinho wanted a League Two move for Mnoga, but the right-back was in favour of a move to Aldershot.
Pompey have agreed a season-long loan deal with the National League side for Mnoga and negotiated a recall clause in his contract.
In the first half of last season, Mnoga was sent out on loan to Gillingham but later recalled by Portsmouth due to a lack of game time.
Now Mnoga will be determined to continue his development with Aldershot Town in the upcoming season.
