•Three types of online video platform engagement are comprehensively investigated.•Social capital was only significant mediator for “sharing” engagement in online video platforms.•Perceived social capital of online video platforms was significant mediator for sharing engagement only for the Generation X and not for the Millennials.•Social values of the online video platforms might not be as important to the Millennials’ sharing video contents. User engagements in video platforms are considered critical for not only businesses in measuring attention, but also for understanding social, cultural dynamics of a form of information platform that has increasingly become influential. For instance, different generations may perceive and engage in online video platforms differently. This study investigates various factors influencing online video platform user engagements in the forms of showing empathy (e.g., “like”), commenting, and sharing. In addition to traditional motivational factors informed by the uses and gratification theory, the study explores how perception of video platforms as social platforms play a mediating role and whether such effects are moderated by generation. A moderated mediation model positing mediating role of social capital and moderating role of generational difference tested against the three types of engagement. Results indicate intriguing generational effect between the Generation X and the Millennials on social capital’s role in online video platform engagement.