Introduction: Social media enable advertisers to promote products by placing ads into videos posted by social media influencers. However, according to psychological reactance theory, any persuasive attempt may evoke reactance. Therefore, how to minimize the audience's potential resistance to product placements is important. This study investigated how the parasocial relationship (PSR) between audiences and influencers as well as the extent to which the influencer's expertise matched the product (termed as influencer-product congruence) shaped audience attitude towards the product placement and their purchase intention through reactance.

Methods: The study conducted a 2 (PSR: high vs low) × 2 (influencer-product congruence: congruent vs incongruent) between-subjects online experiment (N = 210) to test hypotheses. SPSS 24 and PROCESS macro by Hayes were used to analyze the data.

Results: The results demonstrate that PSR and influencer-product congruence enhanced the audience's attitude and purchase intention. Moreover, these positive effects were mediated by lowering levels of the audience's reactance. Additionally, we found preliminary evidence suggesting that PSR moderated the effect of perceived expertise of the influencer on reactance. Specifically, this effect was stronger among those reporting a low level of PSR compared to a high level.

Conclusion: Our findings reveal how PSR and influencer-product congruence are intertwined to shape audience evaluation of product placement via social media and highlight the central role of reactance in this process. This study also provides advice on the selection of influencer when promoting product placement on social media.