The current investigation seeks to explore the impact of perceived authenticity of brands on the motivations for making sustainable purchases from Gen Z consumers utilizing the Meesho social commerce website. The research will examine how both authentic communication from brands and lifestyle orientated marketing strategies lead to environmentally sustaining purchasing behaviour. The data for the study was collected through the administration of a cross-sectional survey using a convenience sample, consisting of 186 completed surveys submitted by Gen Z individuals who utilized the Meesho social commerce platform. The results of the analysis were based primarily on, descriptive statistics, the results of reliability testing (Cronbach's alpha), and correlation and linear regression. Therefore, it can be concluded that while brand association between lifestyle and sustainability behaviour is present. While brand cues increase exposure to and facilitate an average level of behaviour change, they do not have a direct impact on sustainable consumption because of many influences in the external environment. Therefore, social commerce should promote authenticity in sustainability messaging, transparency, and community-driven branding in order to build consumer confidence and encourage responsible purchasing decision-making. In summary, perceived authenticity serves as a behavioural catalyst for - but not the primary driver of - sustainable behaviour within Gen Z.