Purpose - The purpose of this study is to examine the effect of designing anti-stigma posters on the beliefs of students taking the psychiatric nursing course toward mental illness. Design/methodology/approach - This study used a single group pretest-posttest pattern. The study was conducted with 91 students who took the psychiatric nursing course. The data were evaluated using the Beliefs Toward Mental Illness Scale. Students divided into groups exhibited the posters they had prepared in the classroom environment. Findings - It was determined that the difference between the overall score averages of the Beliefs Toward Mental Illness Scale before and after the group studies was statistically significant (p < 0.05). When the overall mean scores of the subscales of Beliefs Toward Mental Illness Scale were examined, it was determined that the "Dangerousness" and "Helplessness and Deterioration in Interpersonal Relationships" subscales had a significant difference between the pretest and posttest overall mean scores (p < 0.05), while there was no significant difference between the pretest and posttest overall mean scores of the "Shame" subscale (p > 0.05). Practical implications - In the process of fighting against stigma on mental illness, it may be recommended to include the practice of designing anti-stigma posters in the psychiatric nursing curriculum. Originality/value - In the study, poster design and protest method was used in nursing education to reduce the stigma toward mental illnesses.