Introducing environmental and sustainability management does not come easy for small and medium-sized enterprises. In particular, they must gain knowledge and expertise to properly implement and manage environmental and sustainability programs, which they often lack the time and resources. Hence, this paper investigates the ability of sustainability-oriented small and medium-sized enterprises to acquire and develop explicit knowledge required for an environmental management system and related tools. By means of qualitative interviews and content analyses, this paper provides greater understanding on the relationship between practices for knowledge development and support factors, including internal capabilities and external cooperation. The results of these qualitative analyses show that certain internal capabilities, including top management support, shared vision, and the room for learning, provide the necessary infrastructure for developing knowledge on environmental and sustainability-related issues in small and medium-sized enterprises. Structured and shared knowledge practices was mostly observed in advanced enterprises, which provide insights for less experienced enterprises to learn and build from.