State-to-state accountability has greatly failed to improve compliance with multilateral environmental agreements. As this is also the case in the Convention on Biological Diversity (CBD), this article explores how and with what effect nongovernmental organizations (NGOs) persuade states to fulfill their commitments to conserve biodiversity. The article conceptualizes accountability as learning-enabling dialogue with the potential to influence state behavior through the provision of constructive criticism. The underlying argument is that NGOs can contribute to overcoming implementation challenges by engaging in constructive dialogue with states. The triangulation of interviews with NGOs, CBD documents, and gray literature suggests that NGOs can challenge or even prevent states’ inertia by establishing critical but cooperative multilevel partnerships with states to advance implementation. Reconceptualizing accountability as constructive dialogue may contribute to realizing the transformative potential of accountability. However, more evidence is needed to understand the roles of NGOs in fostering learning and the impact of learning on improving implementation, compliance, and environmental outcomes.