The online phenomenon of social commerce (i.e., s-commerce) platforms has emerged as a combination of online social networking and e-commerce. On s-commerce platforms, consumers can observe others' behavioural decisions and can distinguish those made by their friends from those made by their followees (i.e., the people a focal consumer follows but who do not follow that consumer back). Given this distinction, our study examines how consumers' behavioural decisions—regarding, for example, purchases, ratings, or “likes”—are made on s-commerce platforms, with a focus on how they are influenced by prior decisions of friends and followees. Combining panel data from a large s-commerce platform and two controlled experiments, we identify a strong normative social influence pattern in which consumers tend to follow others' prior decisions to gain social approval. Because the occurrence of normative social influence depends on both consumer behaviours with high public visibility and strong consumer needs to establish social ties, the unique information concerning behaviour visibility and consumers' social needs in the panel data allows us to identify normative social influence and to distinguish it from informational confounding mechanisms. Our panel data results show that on a friend network, where consumers' behavioural decisions are visible, females exhibit a greater tendency to follow others' prior decisions than males. We attribute this result to the stronger social needs of females. However, on a followee network, where behavioural decisions are invisible, these differences become less evident. Moreover, the two experiments demonstrate that making decision contexts private or activating social needs via a priming procedure can thwart (or even turn off) normative social influence. Our findings challenge prior research that identifies informational social influence as the predominant driver of conformity behaviours and thus have important implications for practice related to normative social influence, such as the development of techniques for satisfying consumers' different social needs depending on their gender or any other situational factors on s-commerce platforms.