Reuben Reid swooped in for an 82nd-minute winner for Plymouth to see off West Country rivals Bristol Rovers.
The on-loan striker powered a close-range header past Rovers goalkeeper Steve Mildenhall from a Conor Hourihane free-kick.
Rovers' Ryan Brunt created the best chance of the first half, but his angled shot was deflected for a corner.
After the break, Plymouth goalkeeper Luke McCormick tipped David Clarkson's shot around the post.
Plymouth's Lewis Alessandra then teed up Rommy Boco, whose 18-yard shot hit a defender and looped over the crossbar. And from the resulting corner, Rovers somehow kept out Neal Trotman's powerful goal-bound header.
Mildenhall denied Argyle targetman Marvin Morgan at the far post following skipper Hourihane's free-kick from the left, before Reid netted late from a quick set-piece from his captain.
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Bristol Rovers manager John Ward told BBC Radio Bristol:
"Even at half time I said to the boys: 'I hope we haven't lost the opportunity to win the game'.
"I saw Plymouth play on Tuesday and they will have seen us on Wednesday and I thought both teams were below those key performances.
"We both played better on those evenings than we were able to today. Going into the first half I thought we could have played better and beaten them.
"We fizzled out at in the top third of the pitch and have not worked the keeper enough times for me to sit here and claim we could have got a draw."