Cops posing as straphangers nabbed two teenage cousins suspected of lifting a decoy iPhone — part of a slick NYPD sting to combat the subway crime wave, officials said.

The undercover cops deliberately placed an iPhone in one of their own backpacks to tempt crooks on an uptown No. 6 train Wednesday, then waited for someone to take the bait.

Soon, the officers noticed Anthony Sander, 16, and William Green, 18, eyeballing the pricey device, cops said.

Green, who lives in upper Manhattan, swiped the phone and passed it to Sander, a West Village resident, cops said during the day yesterday.

It seemed like the alleged crime went off without a hitch — until the duo got off the train at the Morrison Avenue/Soundview station in The Bronx and were arrested for grand larceny.

Neither had ever been busted before, police said.

Sander was released last night without bail at his arraignment.

“This is stupid. I had money in my pocket, I didn’t need to do that,” he said after being sprung.

The charges against Green were dropped due to insufficient evidence, a spokeswoman for the Bronx District Attorney’s Office said.

A woman who identified herself as Sander’s aunt and Green’s mom said, “The boys did wrong. They knew they were wrong.”

“The perp moves in, and then so do we,” the source said.

Cops have recently begun adding more decoys to the subways in a bid to lower crime, which has jumped this year.

Included is a 12.4 percent spike in grand larcenies and a 23.7 percent jump in robberies.