President Trump had better keep an eye on his valuables when he visits New York for the UN General Assembly this week.

NYPD detectives are investigating the alleged thefts of more than $350,000 worth of jewelry from two apartments in Trump Tower, The Post has learned.

It’s unclear if a single thief may be responsible for the heists, both of which were reported to cops earlier this month and are suspected to have been inside jobs, law-enforcement sources said.

“It’s not somebody breaking into the building or roaming the halls, trying the doors until they find one that’s open,” one source said.

Trump is scheduled to speak at the United Nations on Tuesday.

He plans to arrive at his namesake skyscraper at 721 Fifth Ave. — where he owns an opulent, triplex penthouse — at 9 p.m. Sunday, according to the White House.

One victim, a 67-year-old woman who lives on the 42nd floor, told cops she found five gem-encrusted accessories missing from a drawer in her closet, sources said.

The stash, valued at $236,000, included a Harry Winston diamond bracelet and a diamond-and-emerald necklace, sources said.

The woman also said that a pair of earrings, a necklace and a ring — all dripping with diamonds and sapphires — disappeared between June 21 and Sept. 9, sources said.

The other theft involves a $117,000 Graff diamond bracelet owned by third-generation art dealer Isabelle Bscher, who said it was swiped from her 59th-floor pad sometime between Sept. 4 and 9, sources said.

Bscher, 33, runs the Galerie Gmurzynska on East 78th Street.

There was no answer at a phone listed in her name, and a doorman said she didn’t answer when he tried to reach her.

There were no signs of a break-in at either apartment, nor were they ransacked, sources said.

Insurance fraud isn’t suspected, and investigators are compiling lists of everyone with access, including cleaners, contractors and various building workers, sources said.

Additional reporting by Reuven Fenton