This study examines whether sending likes (to followers) increases the likes received (from those followers) in the social networking service (SNS) context. SNS is now considered an essential marketing communication channel, and the strength of the interaction between a firm and customers on SNSs is an indicator of customer engagement. Liking, in particular, is a fundamental reaction in SNS communication, and liking behavior has been interpreted as a gift-giving behavior based on the norm of reciprocity. Thus, previous studies identified a positive correlation between the number of likes given and likes received. However, the causal effect of liking is not yet known. Therefore, this study collaborated with a Japanese consumer goods manufacturer and conducted randomized controlled trials using the firm’s Instagram account. The results do not confirm a causal effect, and we emphasize the importance of impression management theory to conceptualize liking behavior. The findings of this study provide the first evidence for further studies on social customer relationship management and consumer behavior in the SNS context.