The German overcame a nervy start to his final round at the Belmont Country Club to close with a three-under 68 and finish on 19 under par – comfortably clear of Kirk Triplett.
Langer began the day with an eight-shot advantage, and he three-putted the third green to record his first bogey in 48 holes before bouncing back with a superb eagle at the next.
The 57-year-old picked up further shots at the sixth and eighth, and the back nine was a virtual procession as he coasted to his fifth senior major title and his 24th Champions Tour win – matching Miller Barber as fourth on the all-time list.
“I enjoy playing with a big lead. But you’ve still got to pay attention. It’s not like it’s over,” said Langer, who became the first player since Arnold Palmer in 1985 to successfully defend the title. “You just never know what happens. This game is so amazing: It’s brutally tough when things go bad, and enthralling and thrilling when things go right.
“It was a magical week. Obviously, to do something that Arnie did is amazing.”
Triplett won the race for second after firing a sublime 64 that included a run of six birdies in seven holes around the turn.
Meanwhile, Colin Montgomerie fired a commendable 68 to earn a share of third on 10 under despite being admitted to Massachusetts General Hospital on Sunday morning after complaining of chest pains.
The Scot was given the all-clear by doctors and managed to get back to Belmont just ahead of his 1.09pm tee time after his journey was lengthened by a detour caused by a closed bridge.
“I blame the British for building the roads,” he joked before paying tribute to his close friend Langer. “Best of luck to Bernhard. One day it will stop, hopefully sooner than later. But he’s amazing, and all credit to him.”
Montgomerie was joined in a share of third by Joe Durant and Russ Cochran, while two-time US Open champion Lee Janzen warmed up for next week’s major at Chambers Bay with a 68 that lifted him to nine under.