Jon Shaw celebrated his home debut with the only goal as Burton Albion tore up the form book at Eton Park.
The 21-year-old recruit from Sheffield Wednesday struck in the 42nd minute to sentence Exeter to their first Conference defeat in five games since Alex Inglethorpe took the reins at St James' Park.
And it was a deserved first victory in eight league and cup games for Burton, who defended resolutely throughout and always made the better chances.
Exeter looked sharp and bright in the opening 20 minutes, but their pressure amounted to nothing more than a blocked Gareth Sheldon shot and a Les Afful effort that was deflected wide.
In contrast, Burton made decent openings once Shaw and strike partner Mark Robins began to link their moves.
James Bittner was tested by both Andy Ducros and Robins in a blistering spell of Burton pressure and produced an even better save with his legs to deny the former Manchester United star in the 27th minute.
Craig Dudley also had the Grecians keeper back-peddling as an audacious lob dropped just over the crossbar and the Burton goal was overdue when it arrived in the 42nd minute.
Dudley played a key role, first charging down an Alex Jeannin pass and then hitting a low centre for Shaw to tuck the ball inside the near post.
Exeter held the territorial advantage for long periods in the second half, but were rarely encouraged to believe that the Burton defence would repeat its collapse at Forest Green a week earlier.
The visitors' best efforts were from substitute Danny Clay until Burton goalkeeper Dan Crane had to make his only save of the game in added time when he safely held Steve Flack's low shot.
By then, the points could have been safely in the bag for Burton, but Bittner crowned an outstanding display by again denying Robins in the 70th minute.