The alleged sexual abuse happened at the Mejia Family Day Care located on the 2100 block of Pepper Street in Burbank.
According to police, the son of the day care operator abused the 4-year-old male toddler at the facility.
The investigation is ongoing. Burbank police say investigators are conducting a full review of the day care business.
The suspect, whose identity was not released, is currently being held at the Sylmar Juvenile Hall on suspicion of sexual abuse of a minor.
