This article takes the idea of a critical approach to sustainable fashion and applies it to the practices of clothing designers and seamstresses in the Kallio neighborhood of Helsinki, Finland. These practices are described by the umbrella term "sustainable fashion." The main questions are how do clothing designers and seamstresses practice sustainable fashion, what challenges do they face, and how do they interpret these challenges. The article offers an empirical definition of "sustainable fashion," discusses innovative practices of sustainable fashion design in an urban context, considers the tensions within this production concept, and examines ways in which designers address and resolve such tensions. The article contributes to the discussion of a critical approach to fashion, sustainability, and entrepreneurialism in contemporary urban culture.