Critical thinking (CT) has been proposed to be a basic competence in sustainability education to develop students into action competent individuals in complex environmental issues. In sustainability education an interdisciplinary approach is suggested to deal with these complex problems, but in research it is discussed whether CT skills are domain-specific or can be generalized across different school subjects. Therefore, it is of importance to investigate how primary biology and science teachers understand CT in relation to teachers of other subjects. In this study we investigate how Norwegian biology and science teachers in primary schoolunderstand CT. The study design is of a mixed method approach including a teacherquestionnaire from schools all over Norway, and focus group interviews with a sample of teachers. In total, 921 Norwegian primary school teachers answered the questionnaire, of which 135 were science teachers. Of those who completed the survey, teachers from three different schools teaching 5th to 7th grade (N=34), were selected to take part in focus group semi-structured interviews. Descriptive statistics and thematic analysis was conducted. The main findings from the study indicate that the primary biology and science teachers, when compared to other teachers (social science and mother tongue teachers predominantly) view CT as an approach were the teachers should be objective, ignoring values and emotions. The focus of CT among biology and science teachers is on nature of science rather than argumentation, shift in perspectives and source criticism. They focus on the importance to teach about evidence based knowledge with the ability to make predictions, and the difference between science and other belief systems. To conclude, primary biology and science teachers will find it difficult to enact CT within sustainability education themselves if all aspects of CT is to be addressed. These preliminary finding call for a multidisciplinary approach in which biology and science teachers ought to collaborate with teachers in other school subjects when teachingCT in sustainability education with the aim to develop students action competence for sustainability.