A jury found Krystal Khan guilty Tuesday in the death of James Farrior on June 15, 2009.
Prosecutors say Khan took over-the-counter cold medication even though she knew it caused drowsiness and she was supposed to be watching James.
After Khan fell asleep, James tumbled headfirst into a mop bucket containing about 6 inches of water.
The 30-year-old Khan was convicted of reckless assault of a child by a day care provider and endangering the welfare of a child. She faces up to four years in prison at her sentencing next month.
Khan's attorney had said the mother of two was "extremely remorseful."