Purpose – The purpose of this paper is to investigate whether consumers experience territory infringements during interactions with other consumers on firm-managed social media pages and, if so, how consumers respond. In offline contexts, feelings of territoriality affect consumers’ responses to other people in ways that are detrimental to the firm. Less is known about the effects of territoriality in response to consumer-toconsumer interactions on social media. Firms need to understand the implications of these interactions as they encourage consumer engagement on firm-owned social media pages. Design/methodology/approach – The current research examines whether territorial consumer behaviors occur in response to co-consumers on social media pages for a brand (Study 1) and a product (Study 2) using experimental studies. Findings – The studies provide evidence that a perceived territory infringement by a co-consumer can provoke retaliation toward the co-consumer and reduce engagement on the firm-owned social media page. Psychological ownership toward the product or brand amplifies these effects. Research limitations/implications – The findings were robust in the experimental scenarios that featured a brand and a product. However, future research should validate the results in a field study and include other brands and products. Practical implications – The findings highlight conditions under which consumer-to-consumer interactions can decrease social media engagement on firm-owned social media pages. Originality/value – The manuscript is the first to examine how territoriality and psychological ownership relate to negative consumer responses following consumer-to-consumer interactions on social media.