Shelbourne have moved five points ahead of Finn Harps in the battle against relegation at the bottom of the Premier Division.
The Dubliners beat Waterford 1-0 in their clash at the R-S-C on Saturday evening.
Ryan Brennan scored for the visitors in the 84th minute to earn what could be a vital three points.
Shels join Derry City tied for 7th on 16 pts, Harps are second bottom in the play off spot on 11pts and Cork City bottom on 9pts.
Shels have three games left to play while Derry, Harps and Cork have four.