This paper aims to investigate the underlying mechanism of social media on employees' task performance from the perspective of individuals' adaptability to changes. Differing from previous research, this study divides up social media activities. Then, drawing from adaptability theory, we propose that three distinctive social media activities can play a role in individuals' three adaptabilities, respectively. Finally, high individual adaptability can help employees achieve better task performance. The research model is tested using data collected from 210 Chinese knowledge workers who have led or participated in a crowdsourcing project at least once. The empirical results reveal that social connection activities play a positive role in employees' three adaptabilities while entertainment activities play a negative role. Information processing activities are proven to only positively affect cultural adaptability. As we hypothesized, high personal adaptability and interpersonal adaptability do ensure employees' better task performance. What surprises us is that cultural adaptability has an indirect influence on employees' task performance through influencing interpersonal adaptability.