The aim of this paper is to analyze the effect of adaptive investments on international environmental agreements (IEAs) focused on reducing greenhouse gas emissions. It explores the strategic relationships between adaptation and mitigation and their implications for the scope and effectiveness of IEAs. One of the key findings is that adaptation does not improve participation to the agreement. This divergence in results compared to the standard literature stems from a different modelling framework for the terms of the agreement: as in the Paris Agreement, we assume that signatory countries commit to attain a common target, without agreeing to coordinate their actions. This paper broadens our understanding of how various agreement models can impact efforts to address climate-related challenges.