Koscielny played the first 45 minutes against the Foxes at Emirates Stadium but was forced off at half-time after suffering a dead leg in the opening exchanges.
He was replaced by Calum Chambers as the north London side battled back into the game and secured the three points thanks to goals from Theo Walcott and Welbeck.
The former Manchester United striker was making his first appearance of the season following his lengthy lay-off with a knee injury.
And Koscielny was clearly thrilled to see Welbeck secure the win and Arsenal take the three points in such dramatic fashion.
Koscielny tweeted on Sunday afternoon:
Well done gunners well done Mister WELBECK 😃😃 pic.twitter.com/2FNbnKBpWv
— Koscielny (@6_LKOSCIELNY) February 14, 2016
The win left Arsenal two points behind leaders Leicester City heading into the final 12 games of the season.
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