The Hawks led 14-6 at the break after first-half tries by player-coach Paul March and David Clayton.
Tommy Haughey, David March and Richard Knight then crossed in the second half to seal a deserved victory.
That also secured Hunslet's return to the second tier after relegation in 2008 and the club's first championship since 1999, when they were denied a place in Super League.
Hunslet started strongly and took a deserved lead when Paul March crossed from Haughey's offload.
David March kicked the conversion and added two penalties to open up a 10-0 lead.
Blackpool pulled a try back through Casey Mayberry after a Danny Halliwell break.
But Hunslet caught the hosts napping just before the half-time hooter for Clayton to score from Waine Pryce's inside pass.
Haughey extended Hunslet's lead after hacking on a Paul March grubber.
Blackpool got themselves back in it when Damian Munro scored after Martin Ainscough's break, but David March converted his own try.
Luke Haigh was sin-binned and Mayberry crossed before Knight lunged over from dummy-half before Paul Alcock claimed a consolation.
Blackpool: Vaughan, Thompson, Ainscough, Mayberry, Munro, Forber, Hemingway, Holland, Clough, Hobson, Halliwell, McCully, Roberts. Substitutes: Keavney, Anderson, Alcock, Best.
Hunslet: Mark, McHugh, Clayton, Pryce, Grimshaw, P. March, Sullivan, Haigh, Houston, Dooler, Haughey, D. March. Substitutes: Wabo, Lowe, Knight, Woodcock.
Referee: C Sharrad (RFL).