Inquiry-based working by teachers includes working with an inquiry habit of mind, being data literate, contributing to a culture of inquiry at the school level, and creating a culture of inquiry at the classroom level. Inquiry-based working has been found to contribute to educational improvements and the professionalisation of teachers. This study investigates the relationship between psychological factors--attitude, experienced social pressure, self-efficacy and collective efficacy--and inquiry-based working by teachers. Questionnaire data were collected from a representative sample of 249 Dutch teachers. The results show a significant relationship between self-efficacy and all aspects of inquiry-based working. In addition, collective efficacy, attitude and experienced social pressure are all related to aspects of inquiry-based working. School leaders and teacher educators who aim to stimulate inquiry-based working should not only focus on increasing teachers' inquiry skills, but also on psychological factors related to inquiry-based working.