Pompey beat Burton with a performance that was more dominant than the scoreline suggested.
John Mousinho's men had to remain patient against opponents who got plenty of men behind the ball.
But a dinked penalty from Kusini Yengi gave them the lead just before the break, with the Australian striker netting again in the second half.
John Brayford struck late to reply for the visitors, but the Blues saw out the closing stages to secure a 2-1 victory.