Polygyny can be practised formally or informally and it is based on cultural, religious and economic factors. While prevalent in many parts of the world, it raises serious legal, social and ethical problems, specifically about the rights and well-being of women and children. Recent research indicates that Meghalaya has the highest prevalence of polygyny in India. However, there is limited research on the effects of polygynous practices among women whose husbands establish marital relationship with another woman. The study explored the causes and consequences of polygynous unions among tribal women in Meghalaya, using a qualitative study with seventeen women whose husbands had entered into another marital relationship and established a family. Data was collected using in-depth interviews and thematic analysis was employed in analysing the data. The findings revealed that polygyny is driven by disloyalty and lack of marital commitment, men’s inclination towards multiple romantic relationships, religious differences, the absence of strict legal enforcement and community intervention and social passive acceptance. The consequences faced by women were mainly found in psychological, economic and social domains. The study proposes an integrated social work intervention model for empowering women involved in polygynous marriages rooted in rights-based and empowerment-oriented approaches.