Pompey climbed one place to eighth in the standings after seeing off Morecambe at Fratton Park.
The 2-0 victory saw Danny Cowley's side extend their unbeaten run in League One to nine games and keep a fourth successive clean sheet.
Marcus Harness opened the scoring after both George Hirst and Miguel Azeez had been denied in quick succession, while Connor Ogilvie nodded home from a corner.