Lewis McGugan converted a penalty with three minutes remaining to earn Watford a dramatic victory over Doncaster.
McGugan surged through the Rovers defence and produced a fine finish to put the hosts in front.
But Chris Brown drew Doncaster level when he turned in after Manuel Almunia blocked Theo Robinson's effort.
After Rovers' James Husband fouled Sean Murray in the area, McGugan made no mistake from the spot to secure the home side a deserved win.
McGugan joined the Hornets from Nottingham Forest on a free transfer in the summer and put Gianfranco Zola's team in front with an impressive solo effort to beat Ross Turnbull.
Brown equalised with his second of the campaign with he reacted first to the rebound after Almunia failed to hold Robinson's shot.
Doncaster went close to moving ahead when James Coppinger drove just over and Brown headed wide.
But after Husband was penalised for his challenge on Murray, McGugan scored his fourth of the season as Watford won for the first time in five league games.
Watford manager Gianfranco Zola:
"I'm delighted for the three points. I'm also pleased with the way we played in the second half.
"We realised that it wasn't our best day in the first half but we've been patient, waited and went back to basics and started to use the pitch better.
"I think the quality of the football improved and also the chances came, one after the other. In the end we've been rewarded with a penalty but I think the team has done enough to win the game."
Doncaster manager Paul Dickov:
"It's not a penalty. I thought that at the time and after seeing it again, not just once but various times from different angles, I just don't see how the referee can make that call with a couple of minutes left to go.
"I told him it wasn't a penalty. Nine times out of 10 your first reaction is the right reaction and we didn't feel it was, I could tell by young James' reaction that it wasn't and as soon as I've seen the linesman flag for the foul at no point was he going to give the penalty.
"We feel hard done by. We know they're a good team but we defended for our lives. The one thing I don't mind doing is to get beat but to get beat in that manner is a little bit sickening at the minute."