During the early design stages of product-service systems (PSS), particular attention must be given to sustainability considerations to ensure the achievement of a sustainable PSS. However, there is a lack of decision-making support within existing design methods to help designers generating PSS solutions with reduced sustainability impact from the early design stages. To fill this gap, this paper elaborates on a decision support method coupling multi-criteria analysis and sustainability assessment, and considering PSS peculiarities. The aim of the method is to select PSS scenarios with the highest sustainability potential. Sustainability is assessed from multiple perspectives involving both the PSS actors’ points of view and sustainability pillars. The selection of the PSS design scenarios is supported by a multi-criteria analysis enabled by the ELECTRE I method. Furthermore, the paper elaborates on a case study around a PSS-oriented water-saving sanitary equipment intended for healthcare facilities. This provided some evidences of the applicability and relevance of the proposed method, which contributes ultimately to fostering sustainability integration within PSS design.