This study assesses the use of health services among cross-border migrants from Myanmar who are now living in Kanchanaburi Province, western Thailand. The migrants comprise three main ethnic groups, namely the Burmese, Karen and Mon, most of whom have no formal education and are agricultural workers. Results indicate that although the migrants can access government health facilities, they are still more likely to buy drugs or use herbal medicines for treating themselves when they have minor illnesses, while the Thais are more likely to seek medical care from government facilities. The main difficulties for migrants in accessing health services are their legal status, financial constraints, and an inability to speak Thai. Moreover, health beliefs also determine the health-seeking behaviors of migrants, particularly among the Karen who believe in spirits and herbal medicine, while very few of the Burmese and the Mon do so. This leads to the conclusion that ethnicity is an important determinant of the utilization of health services by migrants from Myanmar in Kanchanaburi.