Striker Kevin Phillips climbed off the substitute's bench to score a crucial winner for Southampton.
Phillips struck within three minutes of coming on as a 68th minute replacement for James Beattie and it proved to be enough to settle the South Coast derby.
Wigley came into the game having failed to emerge victorious in ten previous league games since taking over from Paul Sturrock in August and his job was hanging by a thread after Tuesday's humiliating 5-2 defeat at Watford.
Wigley looked as if he would be suffering a miserable Saturday when defender Andreas Jakobsson headed into his own goal to give Portsmouth an early lead.
But teenager Dexter Blackstock levelled soon after with his fifth goal of the season before Phillips headed the decisive goal to leave Wigley punching the air in delight and relief at the final whistle.
Another substitute Jason Dodd, on as a 16th minute replacement for the unfortunate Jakobsson, delivered an inviting 71st minute free-kick into the Portsmouth penalty area for Phillips to give goalkeeper Shaka Hislop no chance with a header inside the right-hand post.
Wigley made five changes from the team that failed so miserably at Vicarage Road, wasting no time in recalling Beattie, Graeme Le Saux and Fabrice Fernandes after they had all recovered from injury.
But his luck seemed out again as Jakobsson's unfortunate own goal gave Pompey the lead.
There appeared to be little danger when Dejan Stefanovic played a long ball down the pitch but the Swedish defender failed to communicate with his goalkeeper Kasey Keller and only succeeded in heading the ball over him and inside the left-hand upright.
Jakobsson suffered concussion in the process and was quickly replaced by Dodd but the veteran full-back's return to the team for the first time since the opening day of the season had the desired effect of motivating his team-mates and they were level within six minutes.
Portsmouth failed to clear their penalty area and Blackstock had no trouble in firing a first-time volley past Hislop.
Keller did well to block efforts from Linvoy Primus and Lomana LuaLua as Portsmouth poured forward in an attempt to regain the lead before half time but it was Southampton who looked the more composed side as the game wore on.
Defender Claus Lundekvam should have headed them in front within five minutes of the restart but sent an unchallenged effort over the bar from Rory Delap's long throw while Hislop had to move smartly to deny Anders Svensson at his near post.
Portsmouth midfielder Patrik Berger was unlucky not to score in the 63rd minute when he let fly with a 25-yard shot which crashed against the crossbar but it was no surprise when Phillips headed Southampton in front with 20 minutes left.
The substitute almost added a second goal with a fierce 20-yard shot six minutes later but Keller had to react quickly with time running out to preserve the home side's advantage after Portsmouth substitute Ricardo Fuller's shot from the left-hand angle looked destined for the top corner.
MAN OF THE MATCH: Kasey Keller (Southampton) - Despite being partly at fault for Pompey's goal the US international produced a string of fine saves on his Southampton debut to help his new side move out of the bottom three.