Purpose: Although the methods and approaches of sustainable design have been developing for more than 20 years, their application in design education and the design process is still under-examined. This study aims to investigate how to integrate sustainability into project-based undergraduate courses in industrial design education, where sustainability has recently been introduced into the curriculum. Design/methodology/approach: Two workshops were carried out as pilot studies within two different elective courses. The scope of the study included sustainable design approaches at both the product and product-service system innovation levels. Findings: The findings show that choosing between the two levels and the sustainable design approach is the most important challenge that students face during the design process. Moreover, the project brief influences the choice of the approach. Originality/value: Following the findings, a sustainable design process model for the project-based undergraduate design courses was proposed. Finally, a new course curriculum on sustainable design was developed based on the findings from the study.