Media programing addressing controversial topics among youth has grown; however, research has yet to consider the correlates of viewing on a global scale. Using the theory of normative social behavior (TNSB), this study examined perceived norms about mental illness among a sample of 3,520 adolescent and young adult viewers and nonviewers of 13 Reasons Why in Australia/New Zealand, the United Kingdom, the United States, and Brazil. We assessed the influence of viewer age and culture on the association between descriptive and injunctive mental illness norms and reports of prosocial mental health-related behaviors (e.g., talking about suicide with others). Results indicated a positive association between the number of episodes viewed and perceived norms, and among viewers, descriptive and injunctive norms related to reports of mental health-related behavior change in all regions, although the process differed based on age and culture. We conclude with implications for the predictions of the TNSB.