Montgomerie's closing round of 67 for a 12-under-par total of 204 was two strokes fewer than his score last year over the same Duke's Course in winning his maiden Senior Tour title.
The Scot had started the day with a four-stroke lead over Mike Cunning, who eventually finished tied for fifth as Montgomerie eased away from the field with a six-birdie, single-bogey round.
The win means the Scot is only the second player to defend the TPM title, has set a lowest winning total in the tournament's history, and is now the fastest Senior Tour player to have won four tournaments (from nine played). And his winner's cheque of €56,376 means he is the first player in Senior Tour history to earn more than €500,000 in a single season.
"It is super to get those records," Montgomerie said. "You never tire of achieving things like that, no matter how old you are. It has been a fantastic season for me. I'm very proud to win this title for a second year, and I'm looking forward to going to Russia to try to win another tournament."