Patience was the order of the day as Pompey applied plenty of pressure on Scunthorpe at a blustery Fratton Park.
They dominated for most of the contest, but it took 71 minutes for the hosts to finally make the breakthrough.
Omar Bogle impressed with a sharp spin and finish, while Jamal Lowe added a fierce second to ensure there would be no late nerves.
Kenny Jackett was pleased that his side got the outcome their display warranted and that they did not hold back after going ahead.
The Blues boss said: “It was a hard-earned result, but a deserved victory for us. We were in control during the first half, but just couldn’t find that final ball.
“There were tough conditions with a bobbly pitch and the wind, but it’s like that all over the country and you have to find a way of adapting.
"There have been too many times this season when we’ve taken the lead and then sat back or rode our luck."
“We had to persevere and it was frustrating at times, although the fans got behind the side very well yet again.
“It was a day when we needed to stick at it and got the key first goal thanks to an excellent finish from Omar. He kept it low and gave the keeper no chance.
“I was pleased with what we did after going in front – we stayed on top and scored another fine effort to run out comfortable winners.
“There have been too many times this season when we’ve taken the lead and then sat back or rode our luck.
“It’s something I’ve been talking to them a lot about – how we can handle the game better. It was a pleasing aspect.
“The result keeps the pressure on the top two. We’ve got 71 points now and there are 24 of them still to play for. We have to keep focused and get as many as possible.”
The only blow for Pompey was Viv Solomon-Otabor limping off just before the break, while Ronan Curtis was not involved after his serious finger injury.
Jackett said: “Viv felt his calf and hopefully it’s not too bad, but we’ll have to wait and see how quickly we can get him back.
“The estimate we’ve heard for Ronan is four to six weeks, but he’s said there’s no way he’s not playing for that long. It’s too early to say about Wembley.”