The Blues bagged a maiden victory at Glanford Park at the fifth time of asking, running out 2-1 winners on Saturday.
Tom Naylor and Gareth Evans scored the visitors'Â goals in the space of six minutes before half-time.
The successÂ moved Jackett's side four points clear of second-placed Sunderland '“Â who were held to a 2-2 draw at Walsall '“Â at the top of the League One table.Â
It looked as though Pompey would ease to victory but Lee Novak's effort on the hour mark gave Iron belief.
The Blues then faced a bombardment of balls coming into their box in the closing stages, with Stuart McCall's side applying the pressure.
But Scunthorpe could not find a leveller, much to the delight of Jackett.
And the Blues boss praised the way his troops stood up to what was a difficult challenge.
He said: 'When they got a goal back there was a succession of free-kicks and they are a very big team '“Â probably the biggest team we have played so far in this division.
'˜You know the ball is going to come into your box, but we defended it well.
'˜If there was any criticism, at the start of the second half we needed maybe a third and fourth goal.
'But in the end we had both a good offensive display and a good defensive display.'
In the 18 games Jackett's men have played in League One this term, they have conceded more than one goal on justÂ three occasions.
And the boss believes an improved defensive solidityÂ is playing a key part in Pompey's push towards the Championship.
Jackett said: 'If you are going to be successful, you need zeros and ones against.
'That will always give you a chance of thenÂ getting some points.
'It always has to be a base. It's not everything, you need more than just that obviously to be at the top end of the table '“Â but it is a base.
'˜This season our goals against column has been good.
'˜It's given us a chance to be able to compete for points all of the time.
'˜But for the majority of the game against ScunthorpeÂ I thought we grew in confidence and looked a good team on the ball.
'˜We just couldn't quite get that third goal, which I felt would have killed them off.
'˜Fair play to Scunthorpe, though, they never gave up.
'We had to then show the other side to our game.
'˜We were organised, resolute and held on to our winning advantage.'