First-half tries to Valentine Holmes and Edrick Lee gave the Maroons the half-time lead.
New South Wales' chances were dealt a severe blow when captain James Tedesco was forced from the field mid-way through the first half with a head knock.
The Maroons dominated the second half with a penalty and a try to debutant Harry Grant.
The Blues were let down by some poor discipline, conceding six penalties and three ruck infringements.
This is the Maroons first title since 2017 and also coach Wayne Bennett's first since 2001.