The Scottish midfielder has had to bide his time since last summer's £3million switch from Hamilton.
But it was worth the wait as his first Premier League goal in the 60th minute set up Wigan's win in an ill-tempered match that saw both sides end the game reduced to ten men with Richard Stearman seeing red for Wolves and Hendry Thomas dismissed for the Latics.
Wigan were well worth their first success in six matches, that was sealed after 73 minutes by the classy Charles N'Zogbia, as they controlled affairs and would have raced to a more conclusive win had Hugo Rodallega - who missed a first-half penalty - been more clinical.
Wolves, who have now lost their last three league games without scoring, never really got into gear as their relegation worries took a turn for the worse and they ended up being booed off the pitch.
Wigan should have really taken a stranglehold on affairs by half-time, but Rodallega could not find a way past Wolves' man of the match Marcus Hahnemann in his personal duel with the American goalkeeper.
Even before Rodallega took centre stage, N'Zogbia had twice wasted two golden chances for Wigan - on the second occasion being denied by Hahnemann following a weak backpass by Kevin Foley.
With Wolves being the lowest scorers in the Premier League, not surprisingly their chances were few and far between.
Crucially, Sylvan Ebanks-Blake threw away their best opportunity of the half in the 19th minute by stabbing wide from just eight yards when he only had Chris Kirkland to beat.
It was a key moment as Wolves never threatened again and that was the signal for Rodallega to begin his battle with Hahnemann.
Twice in the space of 60 seconds he was frustrated by the former Reading keeper.
When he did beat Hahnemann from 25 yards in the 33rd minute his shot crashed off the post.
The Colombian should finally have broken the deadlock from the spot in first-half stoppage time after Stearman needlessly gave away a penalty by pulling down McCarthy as they both chased a ball that was heading out of play.
To add to Wolves misery, Stearman was dismissed by referee Howard Webb having already been booked for an earlier foul on Paul Scharner.
Rodallega struck his spot-kick low and to the right only to see Hahnemann palm it away before Scharner hit the post with his follow-up shot.
While Rodallega could not find a way past Hahnemann himself it was no surprise he was involved when Wigan finally made their pressure pay.
Rodallega saw his shot saved again by Hahnemann but this time the ball ran free to McCarthy - who was also on target in the FA Cup against Hull City – and he made no mistake from eight yards.
While Wolves were given some hope, when Thomas saw red for his second booking in the 67th minute that was quickly dashed when N'Zogbia struck.
Rodallega was again involved, feeding N'Zogbia after Michael Mancienne lost the ball and the former Newcastle United winger weaved his way into box before steering home a low shot.