The visitors went ahead after 15 minutes when Lloyd Davies robbed former Galaxy star Derek Dyker and drove into the box.
He then squared for Craig Thomson whose shot was saved, only for Derry Simpson to score from the rebound.
Lochside were forced into two early changes because of injury and had a penalty appeal turned down when Lloyd Davies made a rash challenge in the box.
Lochside had the next chance of the game when their forward rounded David Jamieson but sent his shot across the face of the empty goal from a tight angle. At the other end Logan Cruickshank forced a great reaction save from the home keeper when he got his shot away inside the box.
The visitors gave themselves a cushion when Craig Thomson scored after good work from Darren Cruickshank.
HT Lochside United 0-2 Fordoun Galaxy
The second half followed a similar pattern to the first with neither team able to string many passes together and Fordoun unable to break down the stubborn Lochside resistance.
The visitors made three changes throughout the half as they tried to close the game out but United threatened too with David Jamieson called into action on more than one occasion.
Lochside ensured a nervy finish when they won a penalty which was scored after some debate as to where the penalty spot should be.
Nine minutes remained but Lochside couldn’t force an equaliser and Fordoun could have made the game safe but Lloyd Henderson could not get enough on the ball as he slid in at the back post.
Fordoun: Jamieson, Davies (Henderson), Mennie, Cuthill, M Deans (Norrie), A Stirling, D Cruickshank, L Cruickshank, Keddie (R Deans), Simpson & Thomson.
League Results from Sunday, February 16:
Bervie P-P Fettercairn
Hillside 1-3 Golf Inn
Hudsons 6-2 St Cyrus
Lochside United 1-2 Fordoun Galaxy
Northern Vaults 14-5 @Bar FC
The Old Bolag 0-4 MCT
Fixtures for Sunday,
Bervie v The Old Bolag
Hudsons v Fettercairn
Marykirk v @Bar FC
MCT v Lochside United
Northern Vaults v Hillside
Jack Bryson Scottish Cup Last 16 (13:30)
Slaemuir FC v Fordoun