Prejudice against elderly people (“ageism”) is an issue of increasing social concern, but the psychological roots of ageism are only partially understood. Recent theorizing suggests that ageism may result, in part, from fallible cue-based disease-avoidance mechanisms. The perception of subjectively atypical physical features (including features associated with aging) may implicitly activate aversive semantic concepts (implicit ageism), and this implicit ageism is likely to emerge among perceivers who are especially worried about the transmission of infectious diseases. We report an experiment (N = 88) that provides the first empirical test of this hypothesis. Results revealed that implicit ageism is predicted by the interactive effects of chronic perceptions of vulnerability to infectious disease and by the temporary salience of disease-causing pathogens. Moreover, these effects are moderated by perceivers' cultural background. Implications for public policy are discussed.