Unlike Friday's mauling of Leicester, an unchanged Pompey team were made to work hard for this result which sees the Blues out of the bottom three of the Championship.
The first half was a scrappy affair with plenty of endeavour but with few clear cut chances. Both sides had tame shots easily saved early on but it was Ashdown who had the first real save to make by rushing out to deny Adamoah at the near post.
David James wasn't a bystander though and he had to palm Mullins' header over the bar when it looked like the midfielder would finally score his first goal for the club, only for his header to bounce off the turf and into Jamo's path.
Jon Stead's curling effort also looked destined for the back of the net but Ashdown did well to turn the ball away for a corner and Dave Kitson probably should have given the home side the lead after James had saved Nugents shot, only for the rebound to be fired over the bar.
James was greeted by rapturous applause when he took his place in front of his goal by the Fratton End and greeted the chants of "Dodgy keeper!" with a wry smile.
He wasn't smiling soon after that, however, as Utaka was given acres of space to cut inside and drill in a 25-yard shot past the ex-Pompey 'keeper to give us an early second half lead. Jamo wasted no time in marching up to his defenders to let them know what he thought of them...
But Pompey felt generous and gifted the Robins an equaliser just two minutes after taking the lead thanks to some slack defending. Adamoah was allowed to cut the ball back for Stead who poked the ball tamely past Ashdown.
The Pompey stopper then had to stop Cole Skuse's long range effort from going in as City began to apply some pressure.
That pressure was seen through by the Pompey defence and it would be one of the back four who would give the hosts the lead again. Aaron Mokoena beat his marker to Liam Lawrence's cross and powered home a bullet header to score his first goal since January.
The lead could have been extended as the excellent Utaka saw his shot go narrowly wide whilst Kitson, who worked so hard all night, had his angled drive saved by James.
Steve Cotterill's men then decided to sit deeper and deeper to defend their lead and I had a feeling that an equaliser was coming. It should have arrived in the 90th minute when Danny Haynes had a free header but managed to put the ball over much to the home fans' relief.
And whilst I was begging for our players to keep the ball in the corner, substitute Kanu had other ideas and put Mullins through to bag his first goal in a Pompey shirt and put the game to bed in stoppage time after a pulsating second half of football.
The Fratton End chanted "Jamo, what's the score?" which was met with another wry smile and some applause as the game ended and confirmed Pompey's second consecutive victory, and well deserved it was too.
It now seems that after a rocky start, the team are settled and are beginning to know each other's games.
Rocha makes a hell of a difference to the defence and Mokoena looks a much better player beside him. Carl Dickinson still has some work to do to convince me that he can be a mainstay in the side but he's beginning to establish himself now.
We have a front two that are willing to work hard for the team and make some intelligent runs and in Liam Lawrence we have possibly the best dead ball specialist in the Championship.
But the biggest factor in this team recently has been the transformation of John Utaka. The man who was booed off on the opening day at Coventry went off to a standing ovation today, not just for scoring a goal but because of his willingness to track back and get stuck in. It's like he is a completely different player!
With renewed confidence the lads can now travel to struggling Middlesbrough believing they can get another win which would take Pompey above the Teesiders in the table.
I don't want to get ahead of myself but I feel that we have finally turned the corner.
Pompey Player Ratings
Jamie Ashdown: 8 - Made some crucial saves.
Joel Ward: 7 - Continues to get better.
Aaron Mokoena: 8 - Great header and did his defensive duties well.
Ricardo Rocha: 8 - Got the majority of his blocks and tackles spot on.
Carl Dickinson: 7 - Setlling in now.
Liam Lawrence: 8 - Some excellent deliveries and set-pieces.
Hayden Mullins: 7 - Finally found the net after good performance.
Michael Brown: 7 - Busy as usual.
John Utaka: 8 - Superb goal, looks like a new player. Keep it up, John!
David Nugent: 7 - Offside flag thwarted clever runs.
Dave Kitson: 7 - Ran himself into the ground.
Substitutes
Darryl Flahavan
Ibrahima Sonko
Matt Ritchie (Utaka 87): N/A - Time-eating change.
Nadir Ciftci (Nugent 79): N/A - Added some fresh legs.
Kanu (Kitson 75): N/A - Brought on to calm the game down and it worked.