With the advent of the Fourth Industrial Revolution, significant use of social network services (SNSs) for career-related purposes has begun to emerge. However, relatively few studies have explored the adverse effects of networking on SNSs, and the existing literature has overlooked its potential consequences. Drawing on upward social comparison theory, this study investigates how networking on SNSs affects career satisfaction through an upward social comparison mechanism leading to ego depletion. To achieve this, we carried out two studies. In Study 1, the hypotheses were tested using a sample of 408 workers. The results indicated that networking on SNSs is negatively related to career satisfaction through a sequential mediation of upward social comparison and ego depletion. In Study 2, we examined this mechanism using a longitudinal design with a three-wave survey of 157 workers, replicating and confirming the findings of Study 1. Both studies demonstrated the process through which networking on SNSs might produce adverse effects on career satisfaction. These findings offer guidance for career counselors, training and development professionals, and managers who want to limit the negative side of networking on SNSs. Different implications for theory and practice are discussed.