Currently approximately 9 million tons of plastic enter the world’s oceans annually. This is a majortransboundary problem on a global scale that threatens marine wildlife, coastal ecologies, human health andlivelihoods. Our concern in this paper is with the environmental governance of marine plastic pollution thatemanates from Thailand, the sixth biggest contributor globally. By zooming in on land-based polluters inThailand, we highlight both the systemic nature of the marine plastic problem and the relative impunity withwhich drivers of transboundary environmental harm function at all levels of governance. Drawing from 19 inter-views conducted with actors from the public, private and non-profit sectors, we examine three stages of theproblem: production, consumption and waste management. We found that three major barriers preventThailand’s government, private sector and citizens from engaging in the sort collective action needed to reducemarine plastic pollution. They are: (i) insufficient incentives to enact political change; (ii) scalar disconnects inwaste management; and (iii) inadequate public and private sector ownership over plastic waste reduction. Asthe state alone cannot change corporate and consumer behaviour, we argue that multi-stakeholder efforts acrossorganisational scales of governance and administrative boundaries are needed to address the barriers