Amateur James Lepp posted a 67 to take second place at 12-under-par 276. Jason Allred, Brad Sutterfield and Clint Jensen shared third place at minus-11. Brad Fritsch and Adam Short finished one stroke further back at 10-under-par 278.
Hearn began the day one shot behind overnight leader Alex Rocha, but dropped in back-to-back birdies from the second to get to minus-13.
The 25-year-old parred five straight holes before a double bogey at the par-3 10th.
Hearn fought back with four birdies over his next five holes. However, he dropped another stroke at the 16th, but closed the tournament in style with a birdie at the last at Gorge Vale Golf Club.
'Wow, it is great to finally get it done, it's very gratifying,' said Hearn. 'Myself, Derek Gillespie and Jon Mills have been good friends for years now, so it means a lot to join them in the winner's circle. Coming close so many times, it sure feels special to win.'
Rocha stumbled to a 3-over 75 to share eighth place with Steve Scott at 9-under-par 279. Chris Wall, Craig Kanada and Eddie Maunder were one stroke further back at minus-8.