A sustainable business model generates a competitive advantage through the incorporation of sustainability at the core of a company. Especially small and medium- sized companies have potential to promote this instrument as they are often seen as the origin of innovative spirit and also account for over 99% of the companies in the EU. This paper showcases and compares two firms, the outdoor clothing producer Patagonia and the sustainable start- up Bureo Skateboards, in regard to their application of sustainable business model innovation. The findings of the two case studies lead to the building of hypothesis regarding the differences between incumbents and start- ups in the development of sustainable business model innovation which can be tested in future research.