Chloe Menager was being held Friday on $1 million bond. Online jail records did not list an attorney for the 25-year-old woman.
The boy was identified as Elijahu Perez.
A police report says Menager caused the death by allegedly holding Elijahu underwater in a bathtub.
Dallas police stopped a vehicle around 4:30 p.m. Thursday, and the driver said he had a call that his son was deceased. Officers followed the man to a residence, where the body was found. The mother was also at the scene.
The father's name hasn't been released.