Aceh, Indonesia, was the hardest-hit area in the December 26, 2004 Indian Ocean earthquake and tsunami, with more than 500,000 people displaced, 120,000 people dead, and total damages and losses estimated at $4.5 billion. The relief effort following the tsunami was also immense, with billions of dollars of aid pledged to this province alone. Since then, there have been several natural disasters, including Typhoon Haiyan, which have caused great loss of life and displacement and for which these results are applicable. This study aimed to determine and assess utilization patterns of health services for children under the age of five with diarrhea, cough and difficulty breathing, fever, or skin disease and to identify determinants of formal and non-formal healthcare usage. A household survey of 1439 households was administered to caretakers of children aged 1–5 years. A sample of clusters within Banda Aceh and Aceh Besar were selected and those caretakers within the cluster who fit the inclusion criteria were interviewed. In the two weeks prior to the survey, 78.3% of respondents utilized formal health services as the first line of care for their child's illness episode. Factors significantly associated with decreased formal healthcare usage for the sick children were if the children were living in a displaced household, if the children's mother or father were not living, and if the children's caretaker was not the mother. Although utilization of formal health services for children was quite high after the tsunami, there were certain children who received significantly less care, including those who were displaced, those who were being cared for by someone other than their mother, and those for whom one or both parents had died. Among the recommendations are suggestions to target these children to ensure that they receive the health care they need.