David Norris curled home an injury-time winner to give Portsmouth a win at Turfmoor this evening.
The victory is also Pompey's first away triumph of the season.
Burnley, who failed to replicate their good recent form - including three successive victories - had an early let-off when Keiran Trippier did well to clear Luke Varney's close-range effort off the line.
The visitors continued to press with little threat coming from Eddie Howe's subdued men and were rewarded in the 91st minute.
Midfielder Norris finished off a flowing move with the finish from just outside the area to ensure that Michael Appleton's men returned to the South Coast with all three points.
Pompey rise two places to 16th while Burnley tumble four places to 15th.
