Migrant network theory is one of the most influential theories seeking to explain how migration happens and how it has been sustained over the past three decades. The theory has been applied to different forms of migration within various geographical contexts and has sparked academic debates on the role and dynamics of migrant social networks. There are some excellent reviews that discuss different perspectives on social networks, social capital and migration in relation to particular author’s empirical research. Yet there is no systematic literature review that brings together the various different dimensions of migrant social networks or the debates related to migrant network theory. This working paper provides a succinct synthesis of the available knowledge on international migration through a social network lens. It is not exhaustive, but it addresses broad topics related to migrant network theory: the role of migrant networks in migration processes; the key debates around and critiques of migrant network theory; the dynamic interactions between meso level migrant networks and macro socio-economic and political structures; and the gendered dimensions of migrant networks. The paper is part of MIDEQ South-South Migration Hub’s research on migration intermediaries; hence, it aims to offer an analytical basis for empirical data collection and analysis by the Hub. It also suggests potential future research directions relevant to both MIDEQ and other researchers.