Critical thinking is generally regarded as one of the most important competences that students should develop in school in order to become contributing members of a sustainable society. This study aims to investigate the link between critical thinking (CT) and sustainable development (SD) in Norwegian and Swedish school curricula. Sustainability issues are often complex and can be seen from various perspectives. This is the reason why a multi- or interdisciplinary teaching approach is mostly recommended in the literature. Regarding CT, there is no consensus on whether it is a subject-specific competence or a general, non-domain-specific, competence and if the criteria on which CT is assessed can vary with the subject. There is evidently a need for cross-disciplinary research to establish what critical thinking competence involves in different subjects and their links to education for SD. A document analysis, based on a framework for sustainability competences, of the general and subject-specific parts of the curricula was therefore conducted in this study. Results show that both the overriding and the subject-specific parts of the curricula, in Sweden and Norway alike, use several formulations linked to SD competences and CT, but only a few of the SD competences are linked to CT competence and directly to SD as content component. This means that if teachers in Norwegian and Swedish schools are expected to teach holistically with a pluralistic approach to sustainability issues inviting critical thinking, they need to make the connections themselves.