Heskey was mobbed by his new team-mates after his debut goal
Emile Heskey scored on his debut as Aston Villa moved up to third in the Premier League table and heaped more pressure on Portsmouth boss Tony Adams.
Heskey smashed the ball home with a first time right-foot strike after Gabriel Agbonlahor's flick-on.
Agbonlahor was later played through on goal but failed to hit the target.
Hayden Mullins narrowly shot over for Pompey, while Peter Crouch missed the target from six yards and Nadir Belhadj saw red after a second booking.
Pompey boss Adams was looking for his team to bounce back from their FA Cup defeat at the hands of Championship side Swansea on Saturday.
His team were the better side for large parts of the game but the facts are that the south coast club have now won just two of 14 Premier League matches since Adams became manager and have picked up just two points from the last 21 available.
It was hardly a vintage Villa performance but, unlike Pompey, Martin O'Neill's team have developed a winning habit.
Villa have now won their last four Premier League games and their last six away from home - and the result at Fratton Park moves them above Chelsea and level on points with Liverpool, both of whom play on Wednesday.
O'Neill accommodated Heskey by deploying him alongside Gabriel Agbonlahor in a 4-4-2 formation.
Adams made four changes from the team that lost to the Swans as he sought to manufacture a change of fortune.
Mullins made his first appearance since his transfer from West Ham, while Kanu made a rare start alongside Peter Crouch up front.
With so many new faces and combinations on display there was little fluency to the opening phase of the match, and Stiliyan Petrov's strike wide of the Pompey goal after 16 minutes was just about the first real attempt on goal.
O'Neill relieved to get three points
Pompey's passionate home support really got behind their team and the players tried to respond, with Mullins' 20-yard shot deflecting off Carlos Cuellar but flying narrowly wide of Brad Friedel's goal.
Villa had rarely suggested they were likely to score before Friedel's long ball was flicked into Heskey's path.
The England international is often accused of not scoring enough but he scored the winner for Wigan at Fratton Park earlier in the season and marked his first appearance for Villa with a crisp finish into the ground and beyond James.
Jermaine Pennant picked out Mullins with a cross from the left and the unmarked midfielder almost emulated Heskey's debut goal but his strike on the turn flew inches over from 12 yards.
Neither side had really taken control but Agbonlahor wasted a great chance to extend Villa's lead when he inexplicably shot wide after the ball had skimmed off Sean Davis's head and given the striker a clean run at goal.
The game became stretched after the break and Villa looked menacing with their attacking pace, while Glen Johnson forced Friedel into action and Belhaj shot wide as Pompey pushed for an equaliser.
Crouch really should have levelled the scores but he failed to hit the target with an instinctive shot inside the six-yard box after Pennant drilled the ball towards him.
Another chance came Crouch's way but he could not keep his header on target and their prospects of taking something from the game depreciated when Belhadj was sent from the field.
Defeated Adams looks to the positives
He might have been given a straight red in the first half after cynically kicking out at Craig Gardner but escaped with a booking.
But he did see red when he was booked for a second time by referee Peter Walton for protesting a decision after he was penalised for handball.
Nonetheless, Pompey continued to press forward but Villa's defence held firm, with Friedel saving at the feet of substitute John Utaka.
Portsmouth manager Tony Adams: "I thought we deserved something. We worked extremely hard and put in a decent performance.
"I asked for a response after the defeat to Swansea and I thought they were excellent. I cannot fault them.
"We have got nothing again but I'm taking the extreme positives out of the game. The fans could see that the boys were giving everything."
Aston Villa manager Martin O'Neill: "It was an impressive debut by Emile and he won the game for us. His whole performance was terrific. I could not be more pleased.
"Portsmouth put us under a lot of pressure but we won the game.
"Although we looked to be out on our feet it was a fantastic effort. The performance epitomised our spirit."
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