Serial pickpockets drove an uptick in crime in New York City’s transit system in 2018, one of the few areas in the city where major felonies increased last year, according to police officials.

The New York Police Department’s chief of transit, Edward Delatorre, attributed the 3.8% increase in crime in the city’s subway and bus system to grand larcenies committed by repeat offenders, including “international pickpocket teams.”

“They’re...