Instagram is one of the social media that is often used in Indonesia. In the business world, Instagram offers promotional solutions with enhanced ad formats and options for targeting and buying. Promotions carried out by business people on Instagram social media add to the special attraction for customers who see it. Warunk Upnormal. Instagram users consider purchasing a product or service viewed through Instagram. This search for information by Instagram users about the product brand they want is what Warunk Upnormal uses to increase the buying interest sought in purchasing decisions. This research was conducted to determine the effect of online promotion through Instagram on purchasing decisions on Instagram followers of Warunk Upnormal. The purpose of this research is to identify and analyze online promotion through Instagram purchase decisions on Instagram followers of Warunk Upnormal. This research is a quantitative descriptive research, this research also includes explanatory research. This study involved 100 respondents who are followers of Instagram Warunk Upnormal. Sampling that will be carried out by researchers is non-probability sampling with purposive sampling technique. The questionnaire in this study used a Likert scale and was distributed online via google form. This study uses SPSS statistical software in data processing. From the results of linear regression analysis, it is known that the independent variable promotion through Instagram (X) has no partial effect on the Purchase Decision variable (Y). And the results of the t-test showed that free promotion through Instagram (X) had a significant effect on the Purchase Decision variable (Y). The results of this study are the Promotion Variables through Instagram are fully included in the good category and overall the purchasing decision variables are included in the very good category on Warunk Upnormal. And it is also explained that the effect of promotion through Instagram on purchasing decisions is 41%. Then, promotions through Instagram can explain buying decisions by 20.1% at Warunk Upnormal. Keywords: Promotion, Social Media, Instagram, Purchase Decision