Monaghan are relegated from Allianz NFL Division One despite this impressive comeback win at Inniskeen.
Farney forward Tommy Freeman blasted in the opening goal before Andy Moran netted to give Mayo a 1-9 to 1-7 half-time lead.
Jason Doherty added the second Mayo goal but Monaghan fought back and Paul Finlay's 11 points secured the win.
Monaghan ended level on points with Armagh but the Orchard men stay up on head-to-head results between the teams.
Mayo spurned two good goal chances before Moran struck just before the break to edge the visitors ahead.
Doherty jinked past two defenders and netted on 52 minutes to leave Mayo three points ahead.
However, Finlay's accuracy from frees proved the difference between the sides as the Ulster side levelled before going on to clinch a two-point victory.