The approach of nursing department students who will practice the nursing profession in the future, which they adopt for individuals with addiction, bears importance. This study was conducted to evaluate the changes in stigmatizing attitudes of nursing students who took the addiction course toward individuals with substance use disorder. The study was conducted in a single group in a pretest-posttest order. Necessary approvals (institution and ethics committee) were obtained to carry out the study. The study sample was made up of 76 students who took an addiction course in the 2020-2021 academic year and who agreed to participate in the research. A questionnaire form and the Alcohol and Substance Addiction Stigmatizing Attitudes Scale were used as data collection tools. Cronbach's alpha value of the scale was found as 0.90. In addition to descriptive statistics, the paired sample t test was used in the analysis of the data from the dependent groups. The mean age of the participating students was 21.2 ± 0.73 years, and 93.4% were female. In the pretest, 10 (13.2%) students reported that they smoked, and seven students (9.2%) reported that they used alcohol. There were no individuals who used any substance other than cigarette or alcohol in the sample. The mean score of the students on the Alcohol and Substance Addiction Stigmatizing Attitudes Scale was 13.89 ± 5.16 in the pretest and 7.34 ± 5.51 in the posttest. This difference was found as statistically significant (p < .01). It was established in this study that the addiction course reduced the stigmatizing attitudes of nursing students toward individuals with substance use disorder.