The present study examined the psychological mechanisms underlying the indirect effects of antidrug-specific social capital on targeted parent-child communication about drugs. Moreover, it explored why campaign exposure and social capital exert interactive influences on parent-child communication. Using a three-round longitudinal panel data set from the National Survey of Parents and Youth (NSPY), we found that when taking into account behavioral attitude, subjective norm, and perceived behavioral control, parents’ attitude toward talking about drugs with their child mediated the effects of antidrug-specific social capital on targeted parent-child communication about drugs. Furthermore, behavioral attitude mediated the interactive effects of campaign exposure and social capital on parent-child communication. The implications of these findings for research on the connection between media exposure and conversation and for public health interventions were discussed.