In a low-scoring affair, it was the visitors who held their nerve to claim victory by a solitary point over Heathens, who remain fifth in the table despite the defeat.
Portsmouth, meanwhile, climbed up a spot to eighth thanks to the win and are now just eight points of sixth-placed Gosport & Fareham 2nds with two games in hand on both them and place-above Ventnor.
After a heavy defeat at city rivals US Portsmouth to kick-off in 2022, Portsmouth 2nds have now secured three successive victories. While out-of-form Fareham Heathens have now lost three of their four fixtures since the turn of the year.