Leading evaluation practitioners were asked about lessons from the recent 26th Conference of the Parties (COP26) for evaluation practice. Contributors emphasize the importance of evaluating equity between rich and poor countries and other forms of climate injustice. The role of the evaluation is questioned: what can evaluation be expected to do on its own and what requires collaboration across disciplines, professions and civil society – and across generations? Contributors discuss the implications of the post-Glasgow climate ‘pact’ for the continued relevance of evaluation. Should evaluators advocate for the marginalized and become activists on behalf of sustainability and climate justice – as well as advocates of evidence? Accountability-driven and evidence-based evaluation is needed to assess the effectiveness of investments in adaptation and mitigation. Causal pathways in different settings and ‘theories of no-change’ are needed to understand gaps between stakeholder promises and delivery. Evaluators should measure unintended consequences and what is often left unmeasured, and be sensitive to failure and unanticipated effects of funded actions. Evaluation timescales and units of analysis beyond particular programmes are needed to evaluate the complexities of climate change, sustainability and to take account of natural systems. The implications for evaluation commissioning and funding are discussed as well as the role of evaluation in programme-design and implementation.