Mikey, a 65-pound, 3-year-old Belgian Malinois, starts his day like most dogs: He wakes up at about 7 a.m., has some breakfast, goes for a nice walk and spends some time playing in the yard.

Then Mikey has to go to work.

Mikey is part of the K-9 unit of the NYPD’s Transit Bureau and works hard, usually on the 11 a.m. to 7:30 p.m. shift, sniffing for things such as bomb-making materials in the city’s large subway system.

He’s one of about 35 dogs that patrol the subway system, and while he works diligently on very sensitive business, at the end of the day he is still first and foremost a dog.

Mikey lives in Seaford, on Long Island, with his handler and NYPD partner, Officer Thomas Regnier.

“He depends on me: I’m the person who takes care of him and feeds him. And we work together. He’s my partner,” Regnier said, adding it can sometimes be challenging. “It’s pretty much like having a kid with us all day.”

Mikey, like many of the NYPD K-9s, was born overseas. The dogs are usually brought into the department when they’re a year old, and then start to train with their handlers.

It took Mikey, who was from Belgium, about four months to learn all of the “typical explosives” that he would need to sniff out. He first joined the department about 2 1⁄2 years ago.

The K-9s can’t rest on their laurels: They get 96 hours each year of additional training to learn how to detect the latest explosive materials that could be used for an attack.

In the Transit Bureau, there are four breeds of dogs: the Belgian Malinois, the German shepherd, a mix of the two large breeds, and two labradors.

As a breed, Belgian Malinois tend to have a high drive, Regnier said, and are perfectly suited to the loud and often distracting atmosphere of the subways.

“They have to have the temperament to be able to recognize that they still have to do the job with all the distractions,” he said, adding: “If he smells a bag or something he thinks he should investigate, I’ll watch his body language.”

Regnier usually has to question people a few times a week when Mikey picks up the scent of something potentially suspicious. Mikey often focuses on items such as printer cartridges or fertilizers, and it’s up to Regnier to determine “when it’s something very serious” or benign.

Typically, when Mikey first gets to work, he and Regnier will stop by a park and throw a ball around for a while.

“So he gets a little excitement and enjoyment first thing,” Regnier said. “We do proactive policing ... We come out and we actually conduct searches of the stations and check for suspicious people, packages, and make sure everybody’s safe for their travels.”

The pair will walk around the platforms and ride the trains, sniffing everything from air vents to a telephone to someone’s bag.

Mikey takes his break at about 3 p.m., heading up to the car for some water and rest.

And when he gets home on a nice day, he gets to run around outside and hang out in the outdoor kennel, checking out the birds and outdoor life.

Mikey was named for Michael Williams, a 25-year-old officer who was killed in a 2014 car crash as he was headed to the United Nations.

“We name our dogs after fallen members,” Regnier said. “It provides a little comfort for the family to help them get through their loss, and [derives a] positive from the negative, so they know that his memory lives on.”

Regnier has small cards for Mikey with his photo and some statistics on it, as well as the story of his namesake. He hands them out to kids, he said, and allows them to pet the calm dog.

Mikey is Regnier’s first K-9 — he patrolled in the 83rd Precinct in Brooklyn before this — and when the dog is ready to retire, he will adopt him.

“I have a wife and three kids and I spend more time with him than I do anybody,” he said. “He’s always with me.”