The purpose of this study is to examine socio-cultural aspects of international migration from Tonga and its impact based on the behavioral approach, which has thus far been neglected in existing literature associated with the country's migration. An interview and questionnaire survey of 150 households from the three island groups in Tonga was conducted. As a result, the following findings were obtained. Household size has recently decreased due to transformation from the extended family to the nuclear family and emigration from Tonga. Consequently, the number of migrants per household is larger than before. The individual or nuclear family rather than the extended family plays a greater role in migration decisionmaking now. With respect to the reason for migration, an increasing motivation to migrate for study abroad since the 1990s is remarkable. Reliance on remittance is not significant partially due to the increase in student migration. Furthermore, there is an obvious tendency for migrants to marry persons with Tongan nationality, and, thus, they are quite likely to settle in their host countries and not return to Tonga.