Against a backdrop of increasing smoke-free policies, electronic cigarette use, and discussion about public health risks posed by smoking and vaping, this study examines psychosocial predictors of intentions to ask others not to use e-cigarettes (vape) and smoke - i.e., assertive communication intentions. A national sample of U.S. adults (n = 474) reported assertive communication intentions for public venues. Psychosocial correlates included perceived risks of exposure to secondhand smoke (SHSe) and secondhand vapor (SHVe), SHSe and SHVe attitudes, subjective norms, and perceived self-efficacy. Separate linear regression models were conducted for smoking and vaping assertive communication intention outcomes. Perceived risks and self-efficacy were associated with greater vaping and smoking assertive communication intentions; subjective norms were only significant for vaping assertive communication intentions. Although a majority of respondents indicated they were unlikely to intervene to voice objections about SHSe and SHVe in public venues, this study suggests that incidental or intentional messages and policies that influence perceptions of risk, norms, and efficacy could affect willingness to voice objections about others' vaping and smoking in public.