Dissertation (MSc Nursing Education)Surgical site infection (SSI) is the most common complication following major surgery, In Tanzania the prevalence of surgical site infection is19% (WHO, 2020). A controlled quasi experimental study was used to assess the effectiveness of vignette teaching technique on improving student nurses competence on surgical site infection prevention which was conducted to 132 third year student nurses whom randomly recruited from different two university schools between July to September, 2020. Participants completed a questionnaire and two cases vignette for each group participants. Data were collected in two phases control and experimental group (pre/post-test) through structured surgical site infection prevention questionnaires and clinical vignette cases presented through video form and case study. Whereby, both descriptive and inferential statistics were analyzed using SPSS version 20. A total of 132 student nurses were enrolled in the study, the mean age was 30 ±22 years. Findings of the study revealed that vignette teaching technique has led increase in knowledge, attitude and practice before the intervention most were in moderate score 70.1%, 46.3%.and 52.2% but after the intervention only knowledge and practice dominating to higher score 56.7 and 52.2% except attitude which are 49.3% that might be due to time in changing attitude to the short time. The paired t-test showed significant difference between pre and post intervention as well as independent test which showed significance between two groups experimental and control group. Subsequently, the linear regression showed a significant association in knowledge change with age (B=-6.201, p<0.001 CI: 0.847, 1.453)and practice change was statistically associated with duration in caring surgical site infection prevention (B= 5.295, p<0.021, CI: 0.806, 1.783). Knowledge, attitude and practice were generally moderate before the educational intervention. However, there was a significant change in student nurse’s knowledge attitude and practice on surgical site infection prevention after an intervention; thus, vignette teaching intervention is effective in the improvement of surgical site infection prevention knowledge among student nurses.