Although they lead to several potential sustainability benefits, product-service systems are not intrinsically sustainable. Therefore, this thesis investigates the factors designers should consider in order to ensure sustainable results. A systematic literature review on product-service system and sustainability is combined with three interviews with product-service system providers. The results are analysed through the application of the Framework for Strategic Sustainable Development. The results of the systematic literature review show that there is no unified definition of sustainable product-service system and multiple approaches to address sustainability in product-service system design. By adopting the Framework for Strategic Sustainable Development, a definition of sustainable product-service system and a list of design criteria are developed. This thesis suggests which overarching aspects product-service system designers should consider to integrate a strategic sustainability perspective. The outcome of this thesis supports designers in understanding what a sustainable product-service system could be and what elements it should embed. By combining the definition and the list of criteria, designers can apply a systematic and strategic approach to integrate sustainability in product-service system offerings.