Background: There is a growing view that 'Big Ideas of science education' are useful for teaching science but there is not much knowledge of how teachers work with them. Purpose: This study explores the conceptualisation and practice of the use of Big Ideas of science education by primary and secondary teachers in Chile. Sample: A total of 63 science teachers (a purposive sample) from pre-school, primary and secondary education in Valparaíso Region in Chile participated in the study, with 38 of them answering all the questions in the research instrument and 25 answering some of them. Design and methods: The research instrument was a questionnaire with open-ended questions. Results: The use of Big Ideas was seen as the 'natural way' to teach science, mostly related to the students' daily lives. Many of the teachers had their own understanding of Big Ideas. They were very positive about Big Ideas, seeing them as a possible way of connecting with the daily lives of students and facilitating progression in students' learning of science. The teachers also saw Big Ideas as enabling students to work collaboratively and make links between different parts of the curriculum, helping them to understand how science works, and preferable to having to teach an overloaded science curriculum that lacks such an organising framework. Conclusion: The teachers were more interested in their own creation and development of Big Ideas rather than simply adopting the existing, official published framework and adhering to what is said in the Chilean curriculum regarding the approach of Big Ideas. These results indicate the need to explore in-depth such varied conceptualisations of schoolteachers regarding the approach of Big Ideas. In turn, this can offer empirical insights into the way Big Ideas are treated in policy documents in Chile and elsewhere.