Willie Bruton and Pauric Fogarty blasted home Limerick 37's first goals from open play this season to secure the Blues second home win on the trot at Jackman Park.
The Shannonsiders got off to the perfect start, with Bruton notching his first goal for the club after latching onto a Darren Harrington through ball to slot home off the post.
Bruton almost doubled his side's advantage minutes later as he came within inches of getting his toe to a low Tommy Barrett cross at the far post.
But the visitors were back on level terms in the 10th minute after Colm Murray's close range header from a Daire Doyle free kick found the back of the net.
Limerick's response was almost immediate with Bruton flashing a low 25-yard drive inches wide of Shay Kelly's right post.
Doyle received a yellow card for bringing down Liam Barrett ten yards outside the box following a fine passing movement from the hosts, but Shane Tracey drove his free-kick off the wall.
Fogarty then collected a wayward Kelly clearance before driving a low shot just outside the post.
At the other end, Darren McKenna was left with too tight an angle to find the target - his header flying back across the goal - after Doyle's corner was flicked to the far post on the half hour mark.
McKenna was then left cursing his luck when his powerful header
from another pinpoint Doyle corner kick came crashing back off the bar.
Lims edged back in front in the 38th minute after Fogarty linked up with Tracey on the left before netting with a low shot from the edge of the box which somehow squirmed between Murray and Kelly.
Limerick goalkeeper Dave Ryan raced swifly off his line to dive bravely at the feet of McKenna eight minutes after the restart, while Kelly returned the compliment to clear from Harrington at the other end.
Harrington almost doubled his side's advantage in the 64th minute but his shot was brilliantly saved by Kelly after Colberts cross was deflected off Luke Kelly into his path.
Murray was left with another free header minutes later, but his connection from a Doyle free kick on the right drifted outside the post.
Bruton almost sealed the win late on, but his rising drive was kept out by Kelly as Limerick pressed for their third goal in injury time.
Limerick 37: Ryan, Daly, Tracey, Danagher, Barrett, L Barrett, Colbert, Harrington (Ryan 74) Hayes (White h/t) Bruton (Cosgrave 90+) Fogarty.
Longford Town: Kelly, O'Donnell (Hogan 69) Frawley, Murray, Casey, Doyle, Hardy, Kelch (Rush 54) Barrett (McCarthy 54) McKenna, Davoren.
Ref: S Grant (Wexford)
