A first half strike from Callum Dingwall gave Formartine their third single-goal victory in eight days, keeping their four-month unbeaten league run intact and their slim title hopes alive.
Formartine coach Jerry O'Driscoll praised the team's growing ability to close games out:
"That's three games on the spin we've won one-nil and it's a good habit to be in. We were not at our best, but I think we deserved the win over the piece.
Deveronvale did have a couple of chances and we were never totally comfortable at one-nil because there is always a chance you can concede. When it is only one-nil you never think you have done enough and there's no margin for error.
However, we have experienced this situation a few times recently and are getting used to seeing the game out. We defended well all over the park and as a team."
A close and hard-fought opening half saw few clear cut chances made at either end, with James McLaren having a goal disallowed for Vale and Conor Gethins and Neil Gauld missing chances for the home side.
United made the breakthrough seven minutes before the break when Gethins and Gauld combined to have efforts at goal blocked, before Dingwall rifled the ball high past Grant Pennet from 15 yards.
An hour in a mistake from Jonny Crawford allowed Callum Murray through on goal, but he could only lob his effort beyond Andy Reid and onto the roof of the net.
Conor Gethins then produced a blistering strike from 30 yards which Pennet somehow managed to divert onto the crossbar and out for a corner.
Vale missed a late chance to grab a point when Pennet's long free kick landed at the feet of defender Steven Davidson, but he screwed his shot tamely wide from 12 yards.
The win keeps Formartine eleven points behind leaders Buckie with two games in hand.