This study aims to examine the impacts of the inquiry learning strategies employed in a "Plastic Education Project" on primary students' knowledge, beliefs and intended behaviour in Hong Kong. Student questionnaires and a test on plastic types were adopted for data collection. Results reveal that the inquiry learning strategies significantly improved students' knowledge of the types of plastic wastes and their corresponding beliefs. However, the strategies seemed not to change students' intended behaviour regarding plastic waste classification and management. The implications of the study for further learning and teaching in environmental education are discussed.