The game was evenly contested overall and the sides were deadlocked at four points apiece at half-time.
Michelle Farrell registered a brace of points in the opening period while Sarah Shannon and Emer Heaney were also on target.
Kildare began the second half in impressive fashion as they opened up a four-point gap in the 44th minute. Lara Gilbert, Lara Curran and Ellen Dowling (two) all kept the scoreboard ticking over.
Michelle Farrell ended Longford’s barren spell when she slotted over a free in the 47th minute but the Midlanders trailed by four points at the second water break.
Brian Noonan’s side raised their game after the resumption and reduced the margin to a single point with seven minutes remaining thanks to a brace from Michelle Farrell along with a point each from Aoife D’Arcy and Emer Heaney.
Longford couldn’t find an equaliser as they lost out by the smallest of margins and Kildare will now play Sligo in the league semi-finals.
