<p><em>Instagram is prevalent in today's digital society, so that it is increasingly being used as a business marketing media. This study aimed to analyze the effect of cost, convenience, influencers, and engagement towards the purchasing decisions. This study conducted to explain the combination of several variables, such as the internal role of marketers represented by influencers, interaction activities on social media that characterized by engagement, and the e-marketing mix approach defined by cost and convenience. The design of this study were quantitative and  cross-sectional study to analyze various variables in the study. The sample was determined using purposive sampling, with 320 respondents. Google Form used to collect data that analyzed descriptively and using Structural Equation Modeling (SEM). This research concluded that influencers significantly affect the engagement and purchasing decisions. Also, convenience and engagement have a significant effect on purchasing decisions. Otherwise, cost has no significant effect on purchasing decisions. The influencer of XYZ should focus on produce content consistently attractive that needed by their target market; maintaining convenience, especially in terms of availability, security, and speed in the purchasing process; and periodically measure the engagement rate (ER) as an evaluation material while convey digital marketing. Influencers also can keep their attention on social media. These things are expected to improve product purchasing decisions in the future.</em></p>