In the final game of the pre-split programme in the Scottish Premiership, McGinn's brace put Aberdeen three points ahead of third-placed Motherwell, as Hibernian increasingly look over their shoulders at a potential relegation dogfight.
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The game saw a frenetic opening on a wet Easter Road surface but there were few chances of note before McGinn opened the scoring on 14 minutes.
The Irishman struck with a fantastic dipping shot from just outside the box, which flashed past Hibernian keeper Ben Williams.
Aberdeen continued to force the pace in an untidy first half and it was McGinn who nearly doubled the lead on 40 minutes, when an excellent passing move ended with his curling shot rebounding off the foot of the post to safety.
That was not the end of the first half near misses, however, and three minutes later Aberdeen hit the post again, when Barry Robson set up Adam Rooney, who also saw his shot kept out by the woodwork.
Hibernian were denied a penalty just before the hour mark, when James Collins was upended in the box.
But it was Aberdeen who deservedly doubled their lead on 62 minutes and killed the game, when McGinn latched onto Rooney's right wing cross to power home an emphatic finish for his 12th goal of the season.