The incident occurred at 1890 Adam Clayton Powell Blvd., near 115th Street, just after 4:30 p.m.
Workers doing construction on the third floor removed walls without bracing the structure, causing a fourth-floor bathroom to cave in to the third floor, Department of Buildings officials said.
There were no immediate reports of injuries, and the people inside the apartment were evacuated.
Gertrude McKenzie, who lives on the fourth floor in the building, was in the shower when she heard a large crack and felt the bathtub begin to lift beneath her feet.
She hopped out of the tub and ran toward her apartment's other bathroom, where she saw that the floor had collapsed, separating from the wall.
"It felt like the whole building was shaking," McKenzie said.
She and her son, Tesfay Farah, said there is now a gaping hole in their apartment, which the DOB vacated for safety reasons.
"There was a giant click and then you heard this big crack and a lot of banging," Farah said. "We went into the bathroom and we could see into the apartment below."
Construction on the third-floor apartment started in December, McKenzie said. Other tenants said there has been a lot of construction in the building.
The DOB issued two violations Tuesday, for failure to safeguard the public and failure to provide a tenant protection plan while performing work in an occupied building, a DOB spokeswoman said.
There is a long history of complaints at the building, including faulty electrical wiring and boiler issues, according to the Department of Buildings website.
McKenzie said about 10 people live in the apartment, including three kids under the age of 6. The family waited for the Red Cross to arrive to help them with housing.
"Where is our family going to go?" asked Christopher Mendez, another one of McKenzie's sons.