A New York City panel voted on Thursday to freeze rents for nearly one million rent-stabilized apartments, fulfilling one of Mayor Zohran Mamdani’s key campaign promises and handing the mayor a major policy win six months into his tenure.

The panel, known as the Rent Guidelines Board, approved the freeze on both one- and two-year leases in a 7-to-1 vote, pausing increases on more than 40 percent of all apartments across the five boroughs — a mix that includes high-rise luxury apartments, deeply affordable subsidized units and 150-year-old walk-ups. New York City now may offer a model for rent control efforts in other cities and states.

“This is a historic victory for New York City tenants,” Mr. Mamdani said in a statement after the vote. He added, “I’ll continue working to deliver a more affordable city by building and preserving affordable housing, lowering building operating costs like insurance and ensuring tenants know their rights.”