Wawrinka, the 2016 winner who missed last year's tournament as he underwent two knee surgeries, swept to a 6-3, 6-2, 7-5 victory on Arthur Ashe Stadium to repeat his opening round triumph over Dimitrov at Wimbledon.
“The last time I played on this great court, I won the title so it was great to be able to come back and play again,” said the 33-year-old Swiss.
“The level was really high, there were lots of emotions out there.
“It's always tough to play your best in the first round.”
Wawrinka, the former world number three, now down at 101, shrugged off having to take a medical time-out early in the third set.
“It was very humid and I felt something. I am just coming back from injury so you never know how your body will react.”
Wawrinka will next face either Ugo Humbert of France or Colin Altamirano of the United States for a place in the last 32.