Objective: This study was conducted to evaluate the effect of Reiki on anxiety, fear, pain levels, and oxygen saturation in open abdominal surgery patients. Materials and Methods: A three-arm, parallel, randomized, and controlled trial design was used in this study. 93 participants were enrolled and randomly divided into three groups (n = 31): reiki, sham reiki, and control groups. All patients in the experimental group, before and after Reiki or Sham Reiki treatments, and all patients in the control groups without any intervention were evaluated with the State Anxiety Inventory STAI-I, with the Surgical Fear Questionnaire for fear of surgery and pain. VAS Scale. Descriptive statistics, t-test, ANOVA, Mann-Whitney U, Kruskal-Wallis H, and Wilcoxon were used in the analysis of the research data. Results: Surgical fear, anxiety, and pain levels decreased, and oxygen saturation levels increased in the Reiki group. The differences between the groups were statistically significant (p<0.005). Discussion: Since Reiki is inexpensive, safe, effective, and easy to apply, it should be administered by nurses to patients who are scheduled for open abdominal surgery.