St. Joseph police were called the home on North 5th Street Friday evening where they found Kion R. Winkfield-Maynard.
Two adults - the baby's father and an uncle - were home at the time. They told police the boy accidentally drowned in the bathtub.
An officer assisted EMS with CPR, but the effort was unsuccessful. The baby was pronounced dead at the hospital.
A medical examiner found no signs of injury or illness. Police stated Tuesday that toxicology reports are pending.
No charges have been filed in the case as the investigation continues.