<p>Aim of this study was to test the immediate effects of a poster with anti-stigma messages on the evaluation of fictitious individuals with gambling disorder in an online experiment. A one-factor between-subject design with four levels was used, in which participants (<i>N</i> = 2,873, 53% female, 45% male, 1.4% diverse, age: M = 44.0 [SD = 17.1] years) were randomly assigned to one of two intervention groups (poster with message 1 vs. poster with message 2) or one of two control groups (poster without message vs. no poster). After a mean exposure time of 14&#xa0;s, participants were presented with a vignette of a person displaying symptoms of gambling disorder. Main outcomes were desire for social distance, perceived devaluation, emotional reactions, assumed dangerousness, blame, categorical thinking, and perceived otherness. In the intervention group, the stigmatisation sum score and three subscales (desire for social distance, sympathy, blame) were significantly lower compared to the combined control group. No differences were found in the amount or quality of stigmatisation between the two intervention groups. Female gender of the vignette moderated effects, with smaller differences for stigmatisation sum score and two subscales (desire for social distance, blame) compared to the male vignette. Given the short presentation time, it is encouraging that the intervention changed stigmatizing evaluations of an individual described as having gambling disorder, although the specific message might not play a role and the interaction with gender must be considered.</p>