Pompey have booked their place in the fourth round of the Emirates FA Cup for a second successive season.
Kenny Jackett's side struck twice in the second half to secure a 2-1 victory over fellow League One outfit Fleetwood at Highbury Stadium.
James Bolton opened his Blues account by bundling the ball home from close range and John Marquis soon doubled the lead, with Conor McAleny adding a late consolation for the hosts.