Resumen: This research focuses on the inquiry methodology for teaching Science in Primary Education text books. This methodology has had a huge reception between scholars and it has been included in curricula such as the Currículo Aragonés. So, first of all, the inquiry methodology is explained, as well as the compatibility between the inquiry methodology and CLIL principles that is discussed to reach the conclusion that the inquiry methodology has a positive influence in promoting CLIL principles. This study sought to analyze L1 and L2 text books, designed for teaching Science, for evaluating the extent to which the inquiry methodology is carried out in Primary Education. The method used for the books’ analysis and evaluation was a quantitative method with some qualitative comments in order to identify the inquiry processes, classify the simple inquiry tasks and evaluate the extent to which the inquiry methodology is implemented in L1 and L2 books for teaching Science. It was showed that the second language or the mother tongue may affect, positively and negatively, Science education with regards to inquiry principles. These principles establish that inquiry tasks must promote cognitive processes, a cooperative environment, production of knowledge and learners’ autonomy. Also, there are other factors that have an influence in the depth to which the inquiry methodology is implemented in Science text books such as the publishing house, author, publication year and other principles and objectives.