While the average time people spend on their mobile apps continues to increase, the life cycle of using new social networking apps (SNA) remains relatively short, mostly due to privacy concern. For SNA users, it is important to know how the perception of anonymity and privacy concern determine the depth of disclosed information. For many SNA developers and practitioners, understanding the actual engagement of users on the platform is critical for measuring success of the app. Previous research has evaluated motivations/preventions of app usage and consequences of continuing usage. Despite efforts to understand the engagement with mobile devices and other users, there is little work in the Information Systems (IS) field to simultaneously investigate the triad of anonymity, privacy concern, and disclosure (APD) on continuous engagement with SNAs. Through the lens of contextual integrity of privacy, this research proposes a research model to investigate APD relationships with perceived and actual engagements with a new SNA. The research model is tested using a survey and actual usage data captured from users’ log files provided by mobile app developers. Results demonstrate how privacy is significantly related with actual engagement while anonymity relationship with actual engagement is fully mediated by perceived engagement.