In an increasingly interconnected world, leakage—broadly understood as unintended displacement of impacts caused by an environmental policy intervention—has become a major governance concern. Yet, leakage remains both loosely conceptualized and poorly understood as a phenomenon in policy making. To fill this gap and broaden the leakage research agenda, we conduct a state-of-the-art review of scientific assessments on leakage (particularly on land use) and combine it with conceptual and analytical frameworks from the environmental governance literature. We then propose a rigorous definition of leakage, discuss frequently overlooked political dimensions, and develop a typology of leakage pathways. Our analysis of leakage through a governance lens yields five core insights: (1) Leakage is not simply a mechanistic phenomenon, but a complex governance issue involving questions of institutional fit, interactions, and political agency. (2) Although the land use literature traditionally focuses on leakage through markets or activity displacement, a governance lens shows that it also occurs through information, motivation, or institutional channels. (3) As policy-makers may act strategically, the unintentionally of leakage should not be assumed but rather become an object of research. (4) A phenomenon not initially regarded as leakage can come to be framed as such through the action of ‘problem brokers’ and changes in policy fields. (5) Policy-makers and researchers should broaden their focus from only avoiding leakage to seeking positive spillovers and institutional synergies. These insights are illustrated with examples from two cases relating to land use policy in Brazil and Southeast Asia.