Langer finished at 11-under 205 at The Woodlands to become the 10th 20-time winner on the 50-and-over tour.
The 56-year-old German player also won the 2007 event at Augusta Pines and successfully defended his title in 2008 at The Woodlands. He opened this season with a victory in Hawaii.
''I'm hoping to add to that number,'' Langer said. ''I hope I'm not done yet. I'm very blessed to have won 20 times in 6 1/2 years. It's been a great run and a wonderful achievement. I just feel like I'm playing some of my best golf in my career.''
Couples, the former University of Houston player who won the 2010 event, finished with a 67. He won in March in Newport Beach, California.
''On a golf course as hard as this, you can't really play relaxed golf,'' Couples said. ''You have to pay attention to what you're doing. I didn't hit enough good shots to shoot a lot lower to catch Bernhard, although I got close to him.''
Colin Montgomerie was third at 9 under after a 70. His best finish on the tour is second in March in Newport Beach. The Scot had no complaints about his finish.
''If you're second, third to Couples and Langer, you're doing OK,'' Montgomerie said.