Manufacturing companies can contribute to a resource-efficient society by designing product-service systems (PSS). Despite the increased importance of PSS for the manufacturing industry in their efforts to become sustainable, few studies focus on small and medium-sized enterprises (SMEs). The study presented in this article aims to add knowledge on how the characteristics of SMEs influence the challenges SMEs experience when designing PSS. It employs a multiple case study design where data are based on interviews, workshops, and internal archive documents from three contract manufacturing SMEs. The analysis suggests that nine SME characteristics influence the challenges SMEs experience when designing PSS. It also shows that SMEs’ different characteristics influence one or more challenges, and that SMEs have a short-term horizon and a reactive business approach which influences the overall challenge of designing PSS.