Gretna picked up their first Premier League away win to make it a double success over Dundee United this season.
Gretna players celebrate Kenny Deuchar's opener
Gretna were gifted an early goal with keeper Euan McLean losing control of a pass-back, allowing Kenny Deuchar to steal the ball and roll it home.
Noel Hunt hit back with a header on 29 minutes but Nicky Deverdics put the visitors back in front before half time with a simple close-range finish.
United pressed throughout the second half but Gretna held on for the points.
Gretna remain rooted to the bottom of the Premier League but have reduced the gap to seven points.
United showed more than the necessary amount of Christmas spirit as they allowed the visitors to settle into the game and presented Gretna with a soft goal.
Deuchar's anticipation was rewarded when he stole the ball from McLean's toes and scored with the minimum of fuss.
Hunt nodded United's equaliser, connecting with Dillon's cross to head past Tony Caig.
The same player then drew a fine save from Caig with a shot from an acute angle, before David Robertson pushed the rebound wide from 18 yards out.
Despite that brief spell of United pressure, it was Gretna who went into the interval in front as Deverdics pounced to knock in a Deuchar header across goal from Horwood's expert delivery.
United took the game to their opponents following the restart but their early efforts were all off target, as attempts on goal from Willo Flood and Garry Kenneth landed wide.
Robson then launched a powerful drive towards goal that was met by a brave block from Collin, before the United captain set up Hunt with a glorious opportunity to once again restore parity.
However, the striker somehow flicked the ball over the crossbar from less than six yards out.
Caig had dealt confidently with everything that United had thrown at him up until the 76th minute, but when he pushed the ball into Robson's path, the Scotland international looked sure to score.
Robson's first touch was good as he created space to shoot but he could then only find the side-netting at the near post.
The home side hurled the ball forwards in the closing stages, but Gretna were not to be denied the victory.
Dundee Utd: McLean, Dillon, Kenneth, Dods, Duff, Flood (Jordan Robertson 66), Buaben (Conway 74), Gomis, Robson, David Robertson, Hunt. Subs Not Used: Szamotulski, Kerr, Cameron, Fleming, Don.
Booked: Hunt, Kenneth.
Goal: Hunt 29.
Gretna: Caig, Cowan (Barr 61), Innes, Collin, Horwood, Deverdics (McGuffie 71), Murray, Skelton, Yantorno, Makinwa (Jenkins 87), Deuchar. Subs Not Used: Fleming, McGill, McLaren, Buscher.
Booked: Cowan, Innes, McGuffie.
Goals: Deuchar 12, Deverdics 42.
Ref: C Richmond