Nadajia Hill, 22, is charged with Kidnapping and Child Endangerment.
Investigators say the baby was taken into Hill's care Friday night. The child's mother contacted police after failed attempts to reach the babysitter.
Investigators say Hill had taken the baby to Newark using public transportation. She and the child were later located traveling southbound on a New Jersey Transit RiverLine train.
Hill was arrested when the train stopped in Riverside just after 12:30 p.m. Saturday.
The baby was found to be in good health and was returned to his family.
Hill was remanded to the Camden County Jail.