This study extends the cognitive mediation model (CMM) by examining the role of social media in cultivating public science knowledge. A sample of 901 Singaporeans was collected through an online survey panel. The results showed that the CMM could be applied to a social media context with a focus on science literacy. Specifically, the findings indicated that people with higher levels of surveillance gratification and social utility motivations tended to pay more attention and to elaborate more about science news that they encounter on social media. Likewise, people with greater social utility motivation tended to engage in greater interpersonal discussions on social media. Notably, attention to news on social media had an indirect association with science knowledge through news elaboration and interpersonal discussion on social media. Implications for theory and practice for science communication were discussed.