Social media platforms expose individuals to both peer and marketer influences. While these influences have garnered significant research attention regarding their impact on consumer behaviors, the findings have been a subject of debate. This research examines how peer influence from user‐generated content (UGC) differs from marketer influence from marketer‐generated content (MGC) in its effect on consumers' eco‐friendly product (EFP) purchases and how peer influence takes place. Study 1 uses online field data from an e‐commerce company and suggests that peer influence is associated with more sales, whereas there is no empirical evidence to support a similar effect for marketer influence. Utilizing online survey data collected from social media users, Study 2 further reveals that informational and normative peer influences significantly increase consumers' purchase intention via environmental self‐efficacy and positive moral emotion. Notably, tie strength with the influencing peer plays a crucial role in moderating the relationship between different peer influences, the mediators, and the mediation paths. Our research advances knowledge of peer influence on EFP consumer behaviors, extends the UGC literature through the lens of peer influence and tie strength, and offers practical implications for social media marketers and policymakers promoting eco‐friendly products.