Critical thinking as a concept, has a rich history and is central to much of the debate within international educational research and increasingly within environmental and sustainability education (ESE). Currently, it is gaining a foothold in the curriculum and in practice in Nordic countries. However, to date, there has been no proper account of what critical thinking entails in formal ESE settings in Nordic countries. In this article, we utilise a theoretically explorative approach to discuss the following research question: "How can various conceptualisations of critical thinking be understood in relation to a selection of ESE positions and current challenges in the Nordic educational context?" Through a theoretical exploration of critical thinking and action in relation to selected ESE positions, we find that although critical ESE positions favour critical thinking, which enables a strong degree of deliberate and detectable action, conceptualisations of critical thinking that promote cognitive skills are also important for critical ESE.