To identify the psychosocial determinants of individuals' intention to engage in collective actions against cancer, we extended and tested the risk perception attitude (RPA) framework at the level of social perceptions. The results of a large online survey of Hong Kong citizens (N = 1,005) revealed that perceived societal risk and perceived collective efficacy directly and jointly influenced respondents' intention to engage in collective actions against cancer, namely donating to cancer charities, volunteering at cancer-prevention organizations, and supporting public policies for cancer prevention. However, the interaction between perceived societal risk and perceived collective efficacy occurred in a direction opposite to the direction in the initial RPA framework. As suggested by the framework, we also categorized individuals into four attitudinal groups based on their perceptions of societal-level risk as well as efficacy and compared their demographic and psychological characteristics. Among the findings, the four groups significantly differed in their perceptions of individual-level risk as well as efficacy, in their family cancer history, and in their intentions to engage in individual-level behaviors to prevent cancer. Altogether, our findings contribute to the literature by extending the RPA framework to individuals' societal-level perceptions and by providing evidence that the framework can benefit the development of health communication campaigns to promote engagement in collective actions to support cancer prevention.