The attorney says the family left just days before a state appeals court appointed a guardian to take over medical decisions for the girl after her parents stopped her chemotherapy treatments.
A hospital in Akron went to court this summer to force Sarah Hershberger to restart her treatments, saying she will die without chemotherapy.
Attorney Maurice Thompson said he doesn't know if the family has returned to the United States.
Sarah's parents stopped chemotherapy because they say the effects were terrible. They wanted to try natural medicines, such as herbs and vitamins.