View the photos from the Blues' Bescot Stadium success
Pompey survived a late Walsall fightback to secure a 3-2 victory and boost their League One promotion hopes.
When Nathan Thompson was shoved inside the box, skipper Brett Pitman stepped up to coolly convert the penalty.
Omar Bogle then found the net via the woodwork, while Viv Solomon-Otabor scored after the break to open his Blues account.
Jon Guthrie converted a couple of late corners to give the Saddlers hope, but the visitors saw out the closing stages.