Objective: To evaluate the effectiveness and safety of ivermectin in patients with mild and moderate COVID-19. Methods: This study was a single-center, randomized, open-label, controlled trial with a 2-arm parallel-group design on 68 patients with COVID-19. According to the 1:1 ratio between the study groups (ivermectin group and standard treatment group), patients were randomly admitted to each intervention arm. Results: The mean age of the participants in the ivermectin group was (48.37±13.32) years. Eighteen of them were males (54.5%) and the participants in the control group had a mean age of (46.28±14.47) years, with nineteen of them being males (59.4%). As a primary outcome, after 5 days of randomization, there was no significant difference between the ivermectin group and the control group in the length of stay in the hospital (P=0.168). ICU admission (P=0.764), length of stay in ICU (P=0.622), in-hospital mortality (P=0.427), adverse drug reactions, and changes in the mean difference of laboratory data had not any significant difference between the two groups (except for urea change). In addition, the radiologic findings of the two groups of patients were not significantly different. Linear regression analysis showed that for every 10 years increase of age, 0.6 day of hospitalization duration was increased. There was no statistically significant association between other variables and clinical outcomes. Conclusions: Among adult hospitalized patients with moderate to severe COVID-19, there was no significant relationship between the administration of ivermectin single dose in a five-day course and clinical improvement, and mortality of the participants.