Despite lagging well behind in the possession stakes at half-time (28%-72%), the hosts led 2-0 at the break thanks to a double from the returning Ronan Curtis.
Pompey were then quick to add to their lead in the second half, with Tom Naylor and John Marquis both finding the back of the net before the hour mark.
Oliver Finney scored a late penalty to deny the hosts a clean sheet but the margin of victory still sees Kenny Jackett’s men move up to fourth in the table.
The wins sees the Blues move up to third in the table – three points behind leaders Hull.
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1. Craig MacGillivray - 8
Two excellent first-half saves from the keeper - and another in the second, even though the flag was up. Photo: JPIMedia
2. Haji Mnoga - 5
(replaced by Callum Johnson on 46 minutes): Found it difficult on full debut, with Crewe looking impressive down their left in that first half. Photo: JPIMedia
3. Jack Whatmough - 8
Magnificent as ever from the classy Pompey centre-half. Photo: JPIMedia
