The baby was discovered in the water in a home.
The mother told officers she was giving a child a bath shortly before 11 p.m. and when she woke up an hour later, she found the baby drowned in the water.
The boy was taken to Trinity Hospital, where he was pronounced dead. The boy has been identified to the Cook County Medical Examiner's Office as Omar H. Annabi.
Chicago police and the Cook County Medical Examiner are investigating.
The Department of Child and Family Services is investigating and said they had no prior involvement with the family.