This paper analyzes the participation of SMEs in production networks, determinants, and policy implications. It finds that although large firms dominate production network engagement in ASEAN economies, there are signs that SMEs have modestly increased their participation since the late-1990s. This is linked to firm-specific factors (e.g., firm size, foreign ownership, skills, technological capabilities, and access to credit) as well as a supportive business environment. Tackling residual supply-side and policy constraints can further the participation of ASEAN SMEs in production networks.