The current Spanish curriculum places considerable emphasis on the development of competences. However, there is a predominance of transmission pedagogies in Spanish classrooms which portray learners as passive receivers of information and there are insufficient opportunities for skill acquisition. Within this scenario, Inquiry Based Learning (IBL) may support Spanish teachers in facing current curricular challenges and in promoting more active, engaging and transferable learning, in mathematics and science. This paper reports on a study involving 47 in-service Spanish teachers. The presentation will particularly focus on the analysis of their beliefs in relation to IBL implementation, as a key issue to address, if a wider uptake of IBL pedagogies is intended. The analysis showed that Spanish teachers saw IBL as an opportunity to engage students in enjoyable learning contexts, although they expressed some concerns in terms of difficulties in classroom management. Generally, they recognised IBL as an interesting approach for competence acquisition and for increasing students’ interest in science and mathematics. However, they claimed that there was a lack of teaching materials and specific professional development courses to support them in IBL implementation, and they worried about not having sufficient institutional support.