NYPD cop Joseph An had an unexpected pair of fans show up as he and 124 other Finest were promoted to sergeant Tuesday.

Brooklyn couple Sasha Cheng, 37, and her 39-year-old husband, Daniel Cheng, surprised the officer, 28, with a bouquet of flower to mark his promotion — one year after the cop jumped into action and got them to the hospital to save the life of their then-unborn baby.

“It was a breached baby,” Sasha recalled to The Post. “It definitely would have been life-threatening for both the baby and myself had Sgt. An not been there at the time. It was through divine intervention.”

Sasha and Daniel Cheng pose with their “guardian angel,” newly minted NYPD Sgt. Joseph An, at Tuesday’s promotion ceremony. Stephen Yang for the NY Post

Their son Royce Cheng is now a healthy 1-year-old.

The Chengs, who live in Bath Beach, were driving to New York Presbyterian Hospital in Lower Manhattan for Sasha to deliver Royce when they got stuck in traffic.

“I think it was like 30, 40 more minutes more before we could get there ourselves,” she said. “We actually saw Officer An’s vehicle, and we pulled over next to him.”

She said she begged him, “Can you please help us get to the hospital safely? I’m in a lot of pain.

The NYPD promoted 125 of New York’s Finest to the rank of sergeant at a department ceremony Tuesday. Stephen Yang for the NY Post

“Sgt. An made a call, and he escorted us to the hospital, and the staff were waiting for us, and the baby was born safely within 20 minutes of arrival.”

For the newly anointed sergeant, it was just another day on the job.

“I just wanted to make sure that I was able to get them to the hospital safely and make sure that everything was OK safely and quickly,” he said humbly. “And, you know, I’m just very grateful to be able to help in that situation.”

An said he’s had many mentors on the job and hopes to be one for younger cops as a sergeant. Stephen Yang for the NY Post

The cop, who is set to marry his fiancée, Ashley Kim, next year, said he was grateful his hard work now has him wearing sergeant stripes.

“You know, I’ve worked heard, and I’m very grateful to be given the opportunity to become a supervisor and basically inspire the minds of cops that I’m gong to be supervising,” he said.

“I had a lot of great mentors, and I want to become a great mentor to the cops that I work with.”

As far as the Chengs are concerned, he’s off to a good start.