The introduction of influencer marketing through the use of social media has affected how marketers market their products. More influencers are being engaged to feature the products on their Instagram accounts or even tag the brand of the products they are using. Besides, young adults are also turning to Instagram as a source of information for their purchasing decisions. Thus, this research aims to study the influence of Instagram macro-influencers as opinion leaders on young adults’ purchase decisions. A quantitative research method was conducted using physical questionnaires. The sampling technique used for this study was convenience sampling, involving 200 participants, both male and female with ages ranging from 18 to 29 years in a private university. The data were analyzed through Statistical Package for Social Sciences (SPSS). Descriptive analysis was conducted to calculate the means, frequencies, and differences of the data. The study found that Instagram macro-influencers have an impact as opinion leaders on young adults’ purchase decisions, with all the mean values of 3.03 and above.