This study proposes to explore the relationship between perceived risk, subjective norm, perceived value, and continuous usage intention via trust as a mediating variable. This research applied a survey which involved 320 IM users (160 from millennials and 160 from Zillennial) in Indonesia. The literature’s existing scales were used to operationalize the constructs proposed in this study. The analyses were conducted using partial least squares structural equation modeling (PLS-SEM) to test hypotheses. The results of the study show that there are differences in the results of the influence of perceived risk on continuous usage intention in the Millennial and Zillennial generations. The results of the study found that continuous usage intention received negative direct impact from perceived risk, positive direct effect from subjective norm, perceived value, and trust on Millennial. In addition, continuous usage intention received negative and not significant direct impact from perceived risk, positive direct effect from subjective norm, perceived value, and trust on Zillennial. The results are useful for instant messaging management into formulating strategies to retain their users in Indonesia. These findings provided theoretical and managerial contributions as well as future research directions.