The amount of internet users in Indonesia grows quickly nowadays. The growth of internet users leads to an increase in online shopping. Today’s popularity of social media becomes a chance for firms to do a business all over the world, including in Indonesia. One of the most popular online commerce media to do business is Instagram. Risks doing online shopping could decrease the consumer’s trust. Therefore, trust is the most important aspect in online shopping. This research aims to analyze the effect of trust on familiarity, information seeking and purchase intention on Instagram. Data was collected through questionnaires that were given to respondents who own an Instagram account and have never purchased any fashion product from an online shop on Instagram. The amount of respondents used to analyze the hypotheses were 201 people. The results of this research show that trust has an effect on purchase intention and information seeking, information seeking has an effect on purchase intention and familiarity, and familiarity has an effect on purchase intention.