This article explores the hypothesis that global inequality may be a central impediment to interstate cooperation on climate change policy. Conventional wisdom suggests that outcomes in international environmental politics are primarily attributable to material self-interest, bargaining power, coercion, domestic environmental values, exogenous shocks and crises, the existence of salient policy solutions, the strength of political leadership and the influence of nonstate actors. Yet none of these approaches offers a completely satisfactory explanation for the long-standing north-south divide on climate change. Drawing on social inequality literature and international relations theory, we argue that inequality dampens cooperative efforts by reinforcing ÔstructuralistÕ world-views and causal beliefs, polarizing policy preferences, promoting particularistic notions of fairness, generating divergent and unstable expectations about future behaviour, eroding conditions of mutual trust and creating incentives for zero-sum and negative-sum behaviour. In effect, inequality undermines the establishment of mutually acceptable Ôrules of the gameÕ which could mitigate these obstacles.