The Blues proved too hot to handle for their Fratton Park visitors as Colby Bishop, Ronan Curtis, substitute Michael Jacobs and Connor Ogilvie cancelled out Joe Ironside’s 30th-minute opener.
The wins means Pompey remain unbeaten in all competitions and move up to third in the League One table.
Here’s how Mark McMahon rated the players’ performance on a pulsating night of action under the lights at PO4.
9. Ronan Curtis - 7
Was fired up for the occasion and endeavour was rewarded with a goal. Photo: NationalWorld
10. Dane Scarlett - 6
(Replaced by Michael Jacobs on 63 mins): Couldn't fault his effort but got no change out of Cambridge defence. Photo: NationalWorld
11. Colby Bishop - 7
(Replaced by Joe Pigott on 72 mins): Took his goal tally to 5 for season. Photo: NationalWorld
12. Louis Thompson - 7
(Replaced Tom Lowery on 63 mins): Picked up the pace of the game with ease. Photo: NationalWorld