In the last two decades, several studies have reported on the benefits of Content and Language Integrated Learning (CLIL) on students' affective and cognitive gains. These studies, however, have mainly concentrated on the implementation of CLIL within the formal (school) context, with very little research on its impact in non-formal (out-of-school) contexts. Thus, the present article addresses this gap by describing an action research project aimed at understanding secondary school students' attitudes towards the integration of CLIL and museum-based pedagogies. The project involved 284 students (14-16 years old) in northern Italy, who participated in a CLIL museum visit on Animal Classification through English at the "Natural History Museum" in Venice. A mixed-method research design was implemented and data was collected through students' questionnaires and focus groups. Results reveal that students showed very positive attitudes towards taking part in a CLIL museum visit based on the interaction among the following dimensions: engagement with museum objects, use of English beyond the classroom, methodology and students' interests, self-concept and career plans.