Although companies have shown a growing awareness of the importance of Corporate Sustainability (CS), integration of CS into their business activities is still problematic. Most of the CS research focuses on large corporations, with limited discussions of Small and Medium Sized Enterprises (SMEs). Research on SMEs has shown that most CS activities have been developed in isolation, and have not yet been totally integrated into the business activities. This research aims to understand how SMEs integrate CS into their business activities. Eighteen SMEs were analysed. These SMEs were, on their explicit request, supported in enhancing the integration of CS into their business activities. The external change agents connected to this consultancy firm applied four CS integration tools, which was based on their own experience in supporting the integration of CS in companies. The data generated through the application of these tools gives this research a specific, external change agent perspective that contributes to the understanding of CS integration. Tables including the tool data of all companies were used to analyse all eighteen cases as well as to enable a cross case comparison. The data showed that a balance proved to be necessary between a physical and social focus in the SMEs' vision on CS, the CS integration activities, the conditions for the CS change agent and the CS assessment. The research also found that although companies in a more advanced CS growth stage have more management system certifications, the management system itself is not used to ensure CS integration.