The striker has 39 Wolves appearances and seven goals to his name after joining the club in January 2016.
Mason, who spent time away with Burton Albion and Colorado Rapids last season, hasn’t featured for Wolves under Nuno Espirito Santo.
He joins a Portsmouth side who’ve enjoyed an unbeaten start to the season in League One, winning four of their opening five fixtures.
Pompey face Plymouth Argyle at Fratton Park on Saturday and Mason will be eligible to feature.