Officers were called around 3:10 p.m. Monday to the Quail Creek apartment complex at 7835 Grow Lane in northwest Houston.
Investigators said people were visiting the woman when they detected a foul smell in the air.
The mother then confessed the source of the odor was the body of her 5-year-old daughter, according to police.
Officers said she claimed the child had died from ingesting chemicals on Aug. 27. The girl's body had been kept in the closet ever since.
Investigators described the body as being in a state of decay when it was found.