Christy Fagan’s first half goal was on the cards for some time as St Pat’s looked the more comfortable side. He found the net on the 34th minute, having been set up by John Russell.
Substitute Jake Kelly ensured the victory with two classy goals in the 83rd and 85th minutes.
The Saints weren’t ready to relax, however, and Greg Bolger piled on the misery, adding a fourth in the 89th minute, to complete a comfortable victory.
Monaghan had a few half chances but Pat’s dominated and Mons are now rooted to the bottom of the table.
MONAGHAN UNITED: C Bennion; R Collins (B Ryan 64), C McMahon, A Byrne, P Whelan; O Humphrey (M Isichei 54), K Quinn, W McDonagh, D Reynor, J Marks; T Griffiths (C Murphy 71).
ST PATRICK’S ATHLETIC: B Clarke, G O’Brien, J Carroll, C Kenna, G Bolger, D Meenan, C Fagan (D Kelly 78), S O’Connor (J Kelly 61), I Bermingham, K Browne, J Russell.
Referee: Neil Doyle