Recent signing Guy Bates scored for the second game in a row to push Drogheda United closer to their first ever Premier Division title.
And his spectacular first-minute strike proved crucial as the Boynesiders’ title rivals kept the pressure on by recording home victories.
The sides went into the game with vastly different recent form – Drogheda had taken three points out of their last 12, while Derry City were unbeaten in eight league matches.
However, Drogheda dispelled any nerves about the health of their title charge within 60 seconds when Barry Molloy bundled over Guy Bates just over 20 yards from the Derry goal.
Englishman Bates, on his full home debut for Drogheda, blasted the free-kick through the defensive wall and in off Patrick Jennings' right-hand post.
Anyone expecting a flurry of goalmouth activity throughout the first half was to be disappointed, however, as much of the next half-hour was played in the central third of the field, with both defences on top.
Eventually a mistake in the Derry defence almost led to a second Drogheda goal as Jennings fumbled Simon Webb's cross and Richie Baker scooped the ball towards goal, only for Ken Oman to clear from under the visitors' crossbar.
In an eventful five minutes for Oman, his short back pass was almost intercepted by Eamon Zayed, he fired wide from 40 yards at the other end and was also yellow-carded for delaying a Drogheda free-kick.
Paul Keegan also threatened from long-range for the Boynesiders at the end of a sweeping move involving five players, but his 25-yard shot flew a yard wide of Jennings' left-hand post.
Drogs keeper Dan Connor, who had been largely untroubled in the first half, was finally extended four minutes after the restart when Killian Brennan's deep cross was met on the volley by Ruaidhri Higgins. Connor instinctively fisted the ball to safety.
The home side were quickly back in the ascendancy, however, and Keegan exchanged passes with Webb before releasing Zayed, who made space before firing straight at Jennings.
With little sign of Derry making a breakthrough, manager John Robertson made two quick substitutions, bringing on Sam Morrow and pushing Gareth McGlynn into attack as the ineffective Mark Farren was hauled off.
However, Morrow lasted just 17 minutes before limping out of the game, leaving Derry short on firepower.
Drogheda nearly took advantage on 72 minutes when Graham Gartland's powerful header was clutched on the line by Jennings.
However, the Candystripes were still very much in the game and Ciaran Martyn sent a shot whistling narrowly wide after being teed up by Brennan.
Connor was forced into late saves from Ruaidhri Higgins and Gareth McGlynn, but Drogheda held on for a priceless three points.
DROGHEDA UNITED – Connor, Shelley, Gavin, Gartland, Webb, Baker, Robinson, Keegan, Cahill, Zayed, Bates. Subs: Keddy for Cahill (71min), Grant for Zayed (89min).
DERRY CITY – Jennings, McCallion, Hutton, Oman, Brennan, McGlynn, Martyn, Molloy, Higgins, Farren, McHugh. Subs: Morrow for McHugh (56min), Hargan for Farren (62min), McCafferty for Morrow (73min).
Referee – Damien Hancock (Dublin).
