PurposeSustainable consumption is an important topic for different industries, including the fashion industry. Despite a favourable attitude of consumers towards sustainable products in the fashion industry, the actual purchase by the consumers is limited. Thus, the present study examines sustainable consumption using the theory of planned behaviour (TPB). The purpose of this paper is to study the mediating impact of strategies of justification of unethical behaviour on the gap-based relationship between a purchase intention and a purchase decision for a consumer in a sustainable clothing context.Design/methodology/approachFor the study, the primary data from 229 graduate-level fashion students enrolled in universities across India has been analyzed with the help of structural equation modelling.FindingsThe study results have proven that attitudes and subjective norms can positively affect purchase intentions when it comes to purchase of the environmentally sustainable products. Further, economic rationality (ER) and government dependency (GD) partially mediate the purchase intention–behaviour gap of the justification strategies for unethical behaviour.Practical implicationsThe results would be helpful in implementing sustainable clothing consumption among Indian consumers. The study would be beneficial for industry professionals, export houses and scholars to discover possible reasons which can lead to the widening of the intention–behaviour gap when it comes to the purchase of the sustainable clothing consumption for Indian consumers. Critical implications for marketers from the present research assert that ER and GD are important factors that could increase the purchase intention of young consumers towards sustainable clothing.Originality/valueThe results of the study contribute to the existing literature in a novel way by adding justification strategies for unethical behaviour to the TPB model. This study is innovative as it adds new constructs to the TPB model by including the three justification strategies that people use for unethical consumption behaviour (ER, economic development and GD) to gain insight into why a purchase intention–behaviour gap exists for sustainable clothing.