Drawing upon cross-national data collected by the International Social Survey Programme (ISSP) across 26 nations and over 28’000 individuals, this study explores the association between climate scepticism and populism in its many forms. Distinguishing between populism’s various ideological dimensions and mechanisms of influence, we find that right-wing and pure forms of populism are linked to greater scepticism and left-wing populism to lower scepticism. Crucially, the impact of populism occurs at both the party (supply-side) and individual level (demand-side), indicating support for theories anticipating both top- down and bottom-up mechanisms of populist influence. Moreover, when combined with globalisation, the link between individual right-wing populism and climate scepticism is further exacerbated. These insights advance ongoing debates by showing that populism is not inherently exclusionary or right-wing, and its diverse forms warrant further exploration.