The Whites had been hoping to avoid defeat on their trip to the South Coast, however a goal on the stroke of half time turned the match Pompey's way.
Dejan Stefanovic headed Harry Redknapp's team ahead after 17 minutes, but moments later Alan Smith chipped Leeds back onto level terms.
Pompey started the brighter with Teddy Sheringham causing Peter Reid's defence problems, after the match was delayed by 30 minutes due to floodlight problems.
Leeds did have chances to go ahead following Smith's equaliser, however Shaka Hislop was in inspired form to deny Seth Johnson on two occasions.
With the teams set to go in level at the break, Pompey caught a break when Gary O'Neil's volley from Gary Kelly's clearance skimmed off Dominic Matteo's back and into the net.
Jermaine Pennant tested Hislop with a right-footed shot shortly after the interval, following good work down the left from Johnson, but then Pompey took complete control.
With the visitors all at sea Hayden Foxe was on hand to volley Sheringham's cushioned header past Paul Robinson's outstretched arms into the far post after 63 minutes. It was four shortly after when a swift break allowed O'Neil to surge past Matteo and slide the ball inside Robinson's right-hand post.
Four soon became five when the impressive Patrik Berger found himself clean through before rounding Robinson and tapping home with his right foot.
Pompey, who had lost their last two league matches 3-0, boosted their goal difference even further when Yakubu was fastest to react to Robinson's superb initial save to tap home from close-range.
