Objectives. To estimate the impact of communicating to the public that men who have sex with men (MSM) are most at risk for mpox on potential stigmatization and risk perception. Methods. We conducted a survey experiment randomizing exposure to messages about mpox among a sample of the South Korean public (n = 1500) in July 2022. We randomized respondents to receive an informational message about mpox that was (1) a neutral informational message about mpox that did not highlight its origins or risk groups (control group), (2) a message explaining that the virus originated in Africa, or (3) a message emphasizing that MSM are most at risk. Results. We found that emphasizing that MSM are most at risk increases support for policies that would restrict lesbian, gay, bisexual, transgender/-sexual, queer or questioning-related events by about 7 percentage points compared with the control condition. However, the message describing African origins did not affect support for restricting travel from Africa. Neither changed risk perceptions or willingness to be vaccinated against mpox. Conclusions. Messages aimed at educating the public about most at-risk groups may trigger increased stigmatization of those groups in ways that could contribute to unnecessary persecution. (Am J Public Health. 2023;113(10):1120-1127. https://doi.org/10.2105/AJPH.2023.307347).