The paper explores whether and under what conditions parties in government influence climate policy ambition. This is examined by an in-depth and comparative case study analysis of four small European states; namely Denmark, Finland, Ireland and Norway. By focusing on small states and the issue of climate change we examine a ‘less-likely’ or hard case of party influence, as both features imply significant external or structural constraints on party influence. We find that government parties’ policy preferences matter for climate policy ambition – and especially under conditions of heightened issue saliency; when the party holds key portfolios; and when the policy does not conflict with their other (e.g. economic or social) policy preferences. As such, the paper lends significant support to the ‘parties matter’ hypothesis, and provides an important contribution by bridging the literature on comparative climate policy and party government.