With the increase in upward social comparison occurring on social networking sites (SNSs) globally, SNS researchers have examined the impact of upward social comparison. However, they focused mainly on psychological outcomes (e.g., well-being). To extend the existing studies, this study investigates the behavioral consequences of upward social comparison through the underlying mechanisms of emotions. Drawing on Smith’s typology of social comparison-based emotions, we developed a conceptual model that integrates upward social comparison on Instagram, upward comparison emotions (upward contrastive emotions and upward assimilative emotions), and the behavioral responses (SNS discontinuance, posting of comments). A structural equation modeling analysis revealed that upward social comparison in Instagram usage provoked upward contrastive emotions including anger, depression, and envy, which, in turn, induced Instagram discontinuance and the posting of malicious comments on Instagram. Additionally, upward assimilative emotions including admiration, optimism, and inspiration triggered the posting of favorable comments on Instagram. This study enhances our understanding of SNS social comparison by revealing how upward social comparison on Instagram is related to behavioral consequences.