After walking the play-off tightrope in recent weeks, the Michael Hall-coached outfit knocked over the highly-fancied The Waratahs 14-12 in a thriller under lights to successfully defend the President's Cup it won in 2018.

But, the decider went right down to the wire.

Following their semi-final loss to the same rivals late last month, the Heelers had plenty to prove on foreign soil.

Muswellbrook hit the front early when centre James Hawkins touched down. Cameron Young piloted the ball through the uprights for a 7-0 lead.

While both teams threw everything at each other for the remainder of the stanza, that score endured until the break.

The Waratahs responded in the second period, via Boyd Chatillon, to trail 7-5.

However, Muswellbrook responded in the best possible fashion when flyer Jason Knox dived over. Young landed conversion number two to extend the side's margin to 14-5.

Just when it appeared the Heelers had done enough, Taunofoa Mosoe found the tryline to give The Waratahs some hope.

Jono Twomey raised the flags for a 14-12 scoreline.

Muswellbrook then hung on to cap off a great season, much to the delight of the hearty band of supporters who ventured down the Hunter Expressway.