Purpose – The main purpose of this study is to investigate the mediating effect of trust on the relationship between consumers’ social motivation and online purchase intentions in the context of social media marketing in the fashion industry of Sri Lanka. Design/methodology/approach – The sample selection was done using a convenience sampling strategy. An online survey was conducted, and data gathered from consumers who worked for a range of organizations, including universities in the Colombo district (Sri Lanka). Findings – The results illustrated that social motivation has a significant positive effect on trust as well as online purchase intentions. And they further demonstrated that a consumer’s level of trust has a significant impact on their online purchase intentions. Trust was also found to partially mediate the relationship between social motivation and online purchase intention. Research limitations/implications – The study was solely focused on the Sri Lankan fashion industry. Consumer behavior relating to other industries may differ. Therefore, this model can be further developed to encompass other industries in future studies. Practical implications – The study contributes to practical solutions in the development of consumer behavior (in the context of social media marketing). Stakeholders in the fashion industry may take the suggestions of this research, such as how to incorporate “trust” in social media marketing to attract and retain customers, into consideration in their future decision making. Originality/value – This study is the first study in the Sri Lankan context to assess the mediating effect of trust on the relationship between consumers’ social motivation and online purchase intentions in the context of social media marketing in the fashion industry of Sri Lanka. Overall,the results offer implications that align with existing theories and contribute to practical solutions in the development of consumer behavior (in the context of social media marketing).