People are known to disclose their private information on social networking sites (SNS) despite their concerns about privacy invasion—a phenomenon referred to as the privacy paradox. Extant studies explaining this paradox have primarily used privacy calculus theory, which assumes individuals rely on reflective factors to make decisions. This theory can well predict the intention of private information disclosure (PID) but lacks the power to explain actual PID. This study follows the reflective-impulsive model (RIM), which encompasses reflective and impulsive systems to explain the actual PID. We collected data from multiple sources to test our hypotheses. We surveyed users of a leading SNS in China, retrieved the messages and photos disclosed by the survey respondents, and invited their SNS “friends” to evaluate these retrieved contents to measure the respondents’ PID. Results support the research model herein: first, in the impulsive system, immediate rewards lead to impulsiveness (compared to long-term social rewards that inhibit impulsiveness), which, in turn, influences PID. Second, in the reflective system, task-focused coping responses mediate the effects of privacy concerns and privacy self-efficacy on PID. Third, the effect of task-focused coping responses under the reflective system contrasts with impulsiveness — the latter being not contingent upon users’ privacy invasion experience. This study contributes to the information privacy literature by applying RIM to explain the actual PID of SNS users and by delineating the different contingent roles of users’ privacy invasion experiences for both systems’ effects.