Galway United
Goals from David Byrne and Sam Verdon was enough on the night and it now means Longford are now within a point of leaders Shelbourne.
The hosts went 1-0 after 11 minutes through a goal from David Byrne after a cross to the far post from Shane Elworthy, which Byrne dispatched.
Seven minutes later, Longford doubled their lead through Sam Verdon, assisted from Aodh Dervin.
On the 55th minute, American striker Shane Doherty, who had only just been brought on halved Longford's lead, as he chipped it over 'keeper Lee Steacy.
Unfortunately, Alan Murphy's side were unable to register an equaliser. It was a weekend of mixed emotion for United, drawing 0-0 on Friday night in Eamonn Deacy Park.
United now drop to third from bottom, two points behind Cobh Ramblers and two points above Athlone Town.
Here is the SSE Airtricity League First Division table currently: