Jamille Matt's second-half goal gave Fleetwood Town a third straight league win of the season as Portsmouth's own recent run of good form came to an end.
The Cod Army looked threatening throughout the match and Matt was denied early in the first half when his low drive was turned onto the post by Pompey keeper John Sullivan.
Sullivan was called into action later in the first period to keep out Antoni Sarcevic's shot and the Fleetwood midfielder was a threat throughout.
Matt's goal on 67 minutes was the result of his burst past young defender Sonny Bradley and although his initial shot was saved, it rebounded off Bradley into the net.
Far from fight back, Portsmouth failed to create clear-cut chances despite starting the game with Patrick Agyemang and David Connolly in attack.
Although Pompey enjoyed slightly more possession, it was Fleetwood who had more shots at goal and arguably looked to more likely to score throughout as a result.
Indeed, Junior Brown had an opportunity to double the visitors' lead but swept wide of Sullivan's right-hand post.
The win sees the Flyde club jump to second in the league table, albeit four points behind Chesterfield.
Chris O'Keefe
