Todd Barranger, Jeff Hart and Darron Stiles finished tied for third at 5-under-par 279.
Hallberg, a three-time winner on the PGA Tour, was 10 shots back as he teed off over two hours before the last group took the course. He was tied for 29th at the start of the round but rocketed up the leaderboard thanks to a brilliant front nine at Glenmaura National Golf Club.
Hallberg birdied the opening hole to move to 3-under. He added back-to-back birdies from the fourth before he made eagle at the par-5 sixth.
The 44-year-old then birdied the eighth to reach 6-under around the turn. Hallberg continued the barrage on the back side with birdies at 10 and 13 until running into trouble with a bogey at the last.
Hallberg was in the clubhouse at 9-under but still trailed overnight leader Joe Daley. All he could do was watch the events transpire.
Daley found trouble often on Sunday but managed to hold the lead until stepping onto the par-3 15th where it all fell apart.
Daley made the first of three consecutive birdies at that hole and closed out his round with a triple-bogey at the last.
Tambellini was tied with Hallberg at 9-under until he played the 18th. The 27-year-old made a triple-bogey of his own and missed the chance to force a playoff.
'I played the last hole poorly,' said Tambellini. 'I spent a lot of money on that hole.'
Hallberg earned his first win on the Buy.Com Tour. He matched the largest come-from-behind victory on tour. The mark was originally set at the 1991 Reno Open when John Flannery came from 10 strokes back to win.
'For the work I've put into my game to pay off is a great feeling,' said Hallberg. 'To play golf and play it well is so much fun.'
The victory was his first since he won the 1992 Buick Southern Open on the main circuit.
Daley finished five shots off the pace after a round of 79. He was joined by Steve Haskins, Ken Green, Arron Oberholser and Bob Friend.
Final results from the NE Pennsylvania Classic