Jordan Everhart was 21 years old when prosecutors say he caused a traumatic head injury after 18-month-old Alaija Corbin wouldn't go to sleep.
He will have to serve 20 years behind bars before he's eligible for parole.
"I apologize for all the actions that have came from me," Everhart said in a brief comment in court.
Police say emergency workers were called to a Boise home after the 18-month-old girl in Everhart's care was reported unconscious. Paramedics reported that they called law enforcement after determining the child had suffered head trauma.
Police say Everhart was babysitting the girl and his explanation for how she was hurt did not match up with the injuries.