This study uses a web‐based randomized experiment (N = 396) to test the effects of message type (narrative vs. expository), stigma (stigmatized vs. nonstigmatized illness), and attribution of responsibility for disease (internal vs. external) on attitudes toward medical cannabis. Narrative‐formatted videos produced more favorable attitudes toward medical cannabis, compared with nonnarrative videos. Effects of narratives on attitudes were mediated through transportation and identification with the protagonist. Participants who viewed narratives in which the protagonist had a stigmatized illness and was responsible for contracting the disease expressed more negative attitudes toward medical cannabis. Effects of attribution were mediated through social distance toward medical cannabis users, and moderated by stigma. Implications for narrative persuasion and public opinion regarding medical cannabis are discussed.