The clothing industry holds huge potential for improvement concerning various aspects of sustainability. Although consumer attitudes towards sustainable products and services, both in general and specifically in clothing, have grown more and more favourable in the past years, the market share of clothing produced in environmentally friendly and socially responsible ways is still lagging behind. This article empirically investigates this phenomenon, known as the attitude-behaviour gap, in the context of sustainable clothing. Based on a large sample of female German consumers, a structural equation model is estimated to assess the magnitude of the attitude-behaviour gap and the impact of possible enablers of, and barriers to, sustainable clothing purchase behaviour. The value-attitude-behaviour hierarchy is used as a theoretical framework, augmented by further psychographic constructs hypothesised to influence behaviour. Apart from a considerable attitude-behaviour gap, the article indicates that a positive attitude towards social-ecological clothing standards, biospheric and altruistic values, as well as an affinity to online and catalogue shopping, enhance sustainable clothing purchases. Egoistic and hedonic values and, remarkably, a preference for durable clothing hinder sustainable clothing purchase behaviour. No significant effects of the suspected barriers – fashion consciousness and price sensitivity – have been identified. The results thus highlight the importance of changing attitudes and values towards sustainability, and of focusing on the durability of sustainable clothing and its availability via retail stores.