The NYPD said Zyaire Crumbley, 18, of Manhattan is under arrest.
According to authorities, police received a 911 call Sunday at 5:40 p.m. about a female who had been stabbed inside an apartment building on Adam Clayton Powell Boulevard.
Upon arrival, police found Saniyah Lawrence, 16, with a stab wound to her neck.
EMS rushed her to NYC Health & Hospitals/Harlem, but it was too late to save her life.
The NYPD later announced that they were looking for Crumbley in connection with the killing. He was arrested late on Monday. Crumbley was Lawrence's boyfriend of more than a year, police said.
It was unclear if he had a lawyer who could speak on his behalf.