It was a remarkable turnaround for the traditionally slow-starting Cowboys, who had conceded the first points and the first try in seven straight games.
In contrast, the resurgent Sharks - the 2014 wooden spooners - had scored the first points in nine of their past 10 games.
North Queensland hit the ground running in Townsville, grabbing a 19-0 halftime lead and never looking back.
Pivot Michael Morgan had beat himself up during the week for not providing enough support for playmaker Johnathan Thurston in a quiet return from an ankle injury in last week's 16-12 finals loss to Brisbane.
He vented his frustration on the Sharks, opening the scoring before completing a try scoring double in the 46th minute.
Morgan set the tone when he latched onto a Thurston cut-out pass and brought the Townsville fans to their feet by scoring in just the fifth minute.
North Queensland romped to a halftime lead thanks in part to Cronulla's 16-2 missed tackle count.
The Cowboys kept their perfect finals record in Townsville (6-0) intact.
Cronulla have never won a final outside Sydney.
North Queensland won a season best 17 games this year including a club record 11-game streak.
But there was a debate that North Queensland - who went on a club record 11-game winning run this year - had peaked too early this season.
The win over Cronulla put an end to any doubts over their title credentials.
- AAP
