An octogenarian serial burglar who’s eluded capture since 2014 — thanks to his unassuming grandpa look — has finally been nabbed by the NYPD after making off with nearly half a million dollars in loot, authorities said Tuesday.

Samuel Sabatino, 81 — who’s described by police as an “unassuming,” “old-school crook” — was caught on Saturday and charged with five counts of residential burglary for a string of recent break-ins — though cops are working to link him to dozens of other crimes he’s suspected of committing on the Upper East Side, officials said.

“This investigation has been going on for several years. There’s countless videos that we’ve been going through. It keeps getting better. There’s so much at our fingertips,” NYPD Detective Kevin Gieras, who’s been on the case since 2014, told The Post.

Police said Sabatino, who’s old enough to remember FDR’s presidency, leaned on his seemingly ordinary look to slip in to luxury, doorman buildings undetected and usually struck over holiday weekends when wealthy Manhattanites were out of town.

“His M.O. is coming in and preying on victims while they were away. He’s an older gentleman who enters these buildings. He’s able to get past these doormen by the way he looks and the way he acts,” Gieras explained.

Once Sabatino got in, police said he’d try “all the doors” and when he found one that was open, he’d go in and grab anything of value he could find — usually pricey jewelry and watches.

Most recently, Sabatino is accused of breaking into an apartment on East 68th Street over the Fourth of July — where he allegedly snatched “multiple high-end watches” with an estimated value of approximately $39,000, prosecutors alleged in a criminal complaint.

Over Memorial Day, Sabatino allegedly hit an apartment on East 79th Street and made off with more than $50,000 in property, including wedding rings, a diamond ring and more pricey watches, prosecutors said.

But police believe his spoils are much larger than what he plundered this year and believe his total bounty amounts to at least $400,000 worth of goods.

On Tuesday afternoon, The Post discovered nanny-cam video released by cops in 2015 which shows who they believe to be Sabatino pilfering a home on East 86th Street on July 4, 2015.

In the clip, an elderly man with glasses wearing a black, Puma hat and a smart black jacket is seen rummaging around a bedroom.

During that hit, the suspect in the video managed to break into three apartments and stole jewelry from each one, police said.

Gieras, who was thrilled to finally see Sabatino in cuffs, said the alleged thief was dubbed the “July 4th Burglar” because of his tendency to hit apartments over the patriotic holiday — but once he was arrested, the name took on a whole new meaning.

Not only was July 4th one of Sabatino’s choice days for burglaries, it’s also his birthday, Gieras said.

“When he told me that was his birthday, I was like, ‘No way,’” the detective said.