Since regulations require paid promotions to be disclosed, consumer awareness of advertisements has changed. That requires more focus on assessing influencing factors when it comes to evaluating the effectiveness of an advertisement. This empirical study investigates the effectiveness of advertisements based on the type of influencer and product illustration on an Instagram Story. An experimental design with a total of 308 participants is used to examine consumer attitudes toward advertisements and purchase intention. In addition, the mediating role of source credibility is investigated. The findings show that a product, advertised in a context-based setting on an Instagram Story, has a positive effect on consumer attitude towards the advertisement and their purchase intention. There is no significant effect in the use of a micro-influencer compared to a macro-influencer. In terms of advertisement effectiveness, source credibility can be identified as a mediator for positive consumer responses.