The purpose of this study was to analyze the relationship between Social Media Marketing and Brand Image, Social Media Marketing relationship and Purchase Intention, Brand Image Relationship and Purchase Intention and finally, the relationship between Social Media Marketing and Purchase Intention through Brand Image. The approach in the research used is a quantitative approach using PLS-SEM SmartPLS software as a data processing tool. In this study, the data collection technique was carried out using a questionnaire or online questionnaire which was distributed to 234 respondents of Millennial Smartphone Consumers in Banten Indonesia. Sampling system was accomplished with a snowball sampling method. Based on the results of hypothesis testing, it was found that there was a positive and significant relationship between Brand Image (BRI) and Purchase Intention. There was also a positive and significant relationship between Social Media Marketing and Brand Image. However, there was an insignificant relationship between Social Media Marketing and Brand Image while there was a significant relationship between Social Media Marketing and Purchase Intention through Brand Image as Mediator.