In this study, the impact of the reasons for leaving their country (such as social, economic, and political) of Afghan asylum seekers who illegally entered Turkey from the eastern border on their life satisfaction in the country of destination was analyzed. The sample comprised 500 individuals (54.8% women; 42.4% < 30 age) who came as refugees from Turkey’s eastern border. Three-stages of analysis were carried out in the study: the Mantel–Haenszel test, ordered logit, and CART (Classification and Regression Trees) decision tree. The main findings obtained from these analyses show that individuals leaving their country for economic reasons and because of war/terrorism are happier, while those leaving their country because of religious and cultural pressures are unhappier. According to the results of the CART analysis, the most frequently repeated variables are economic and life satisfaction of individuals who are satisfied with their household income and save money is at its highest level. In the analysis it is also seen that the life satisfaction level of individuals who are not satisfied with their household income, leave their country for reasons other than economic reasons, and make a living on debt is very low. This study also focuses on the relationship between happiness and sustainable development (SD). It has associated the reasons for migrants leaving their countries with the Sustainable Development Goals (SDGs), highlighting the significance of happiness studies in achieving the SDGs.