Ian Sharps's header secured three points for Rotherham United at the expense of play-off rivals Exeter City.
The Millers defender glanced home a corner from Ben Pringle just before half-time, after Alan Gow earlier struck the crossbar for the hosts.
Mitchell Rose was sent off in the second half for a foul on Aaron Dawson to leave Rotherham down to 10 men.
Despite Grecians pressure, Andy Warrington was comfortable in the visitors goal, saving from Matt Oakley.
VIEWS FROM THE DRESSING ROOM
Exeter manager Paul Tisdale told BBC Radio Devon:
"I loved the game today and I have no criticism of the players' commitment.
"We conceded the first goal and it becomes so hard to score.
"Going into the second half of the season, we need to make sure it happens less frequently than it has done this season so far."
Rotherham United manager Steve Evans told BBC Radio Sheffield:
"The rollercoaster continues, we've had the good, the bad and we've not had the ugly yet.
"The ugly is when you don't play particularly well (and win).
"It's a big win, you have to respect Exeter as a team and the manager. They've beaten Bradford away and the league leaders.
"We said to the players, we would settle for a thoroughly professional 1-0 victory where we worked hard and had a disciplined shape."