In a statement to ABC News, Sununu said he hurried to help the Hampton Beach Lobster Roll Eating Competition participant after he noticed he was choking.
"In the commotion and excitement of the contest, I was the first to notice that the gentleman at the far end of the row of contestants was choking. So, I moved forward and immediately started giving him the Heimlich," Sununu said.
The contestant, Christian Moreno, had begun tapping on his chest to indicate he couldn't breathe, according to New Hampshire ABC affiliate WMUR.
Sununu gave Moreno four or five abdominal thrusts before emergency responders jumped in, continuing the Heimlich maneuver until the chunk of lobster was dislodged from his windpipe.
Despite the dangerous medical incident, Moreno didn't give up on the seafood eating competition.
"After the lobster roll was dislodged Christian went right back to the contest, which I couldn't believe," Sununu added. "He ate another seven lobster rolls after that!"
Moreno told WMUR he was not wearing his glasses at the time of the incident, so he did not initially realize it was the governor who had come to his rescue.
"My counter came up to me and, like, made a joke. And was like, 'Oh, like, I bet nobody else can say that they've gotten the Heimlich from the governor before,'" he said. "And I looked at him, was just like, that was, that was the governor?"
Moreno lost the contest, but vowed to try again next year.
"I will be there for my redemption, 100%," Moreno said.
Sununu said he was grateful to the first responders who treated Moreno.
"Here in New Hampshire we never hesitate to jump in to help," he added. "I'm just glad I paid attention in my high school health class."
Sununu, 49, is a rising star in the Republican Party and flirted with running for president in 2024 until blaming a "crowded field" for his decision to hold off. He's been governor of New Hampshire since 2017.