Bangladesh is one of the most child marriage prone countries of the world. The causes of child marriage in Bangladesh are multidimensional. Although marriage is a social bond between a male and female, the issue of child marriage has become a social disease. However, the main purpose of this study is to explore the causes of child marriage from theoretical point of view. Methodological mixes have been applied in this study. For understanding the research problem comprehensively, social survey as a quantitative method and focus group discussion, case study, and document analysis as qualitative methods has been used. Both male and female children of the study area were the respondents of the study. Snowball sampling techniques have been applied in this study. The findings of the study identified thirty four causes. These are: Cultural tradition, strong religious beliefs, social insecurity, poverty, lack of education and consciousness, patriarchal society, dowry, over population, under-empowerment of woman, considering girls as burden to the family, remote location, lack of social mobility, drop out, illiteracy, girl’s beauty, customs, autocratic behavior of parent and other guardians, getting a better bridegroom, weak local government, strong communal solidarity, social pressure and audience challenge, fear of social stigma and self-esteem, lower scope of higher study, romantic relation, eve teasing, rape, misconception about reproductive health, abuse of information technology, competition and conflict with neighbor, considering girls as fresh, young and innocent, lack of activities from the central government, possibility of losing market value, preserve land property. In this paper an attempt has been made to explain the causes of child marriage through major sociological theories. The findings of the study may be helpful for the academicians as well as the policy makers to suggest appropriate plans and programs for controlling child marriage with a view to achieving sustainable development goals.