AFC Telford United defender Shane Killock's stoppage-time own goal ended Forest Green's seven-match winless streak.
Charlie Griffin put the hosts in front before half-time when he slotted home from 12 yards.
Adam Proudlock thought he had secured a point for the Bucks when he headed in Greg Mills' cross 13 minutes from time.
But Forest Green snatched a dramatic win when Killock sliced James Rowe's corner into his own net.
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Forest Green Rovers manager Dave Hockaday told BBC Gloucestershire:
"We didn't play anywhere near as well as we had in the past three games and yet we get the three points.
"I'm really happy with the result and the fact that we kept on going.
"We didn't play as well as we have been, or as we can, but we'll take that for spirit."