Objective: This study was performed to compare the perception of pain between patients treated with passive self-ligating fixed appliances and those treated with Invisalign aligners. Methods: This prospective study conducted in Saudi Arabia used an estimated sample of 64 patients from a private dental clinic. After obtaining written informed consent, the patients were divided into two groups; one group (n = 32) was treated using passive self-ligating fixed appliances and the other group (n = 32) using Invisalign？？ aligners. Immediately after fitting the appliances, the patients’ perception of pain was evaluated through a closeended and coded self-administrated questionnaire by using a visual analog scale (VAS). Their responses were recorded at 4 hours, 24 hours, day 3, and day 7. Mann-Whitney U-test, Kruskal-Wallis test, and Pearson’s chi-square test were performed for statistical analysis. Results: A lower percentage of patients treated with Invisalign aligners reported pain than did patients treated with passive selfligating fixed appliances, and these differences were statistically significant (p = 0.001). Similarly, the mean VAS score for the Invisalign group was significantly lower than that for the passive self-ligating fixed appliance group at different intervals during the first week of treatment. The intensity of pain with both appliances peaked at 24 hours (mean VAS score, 3.87) and was lowest (mean VAS score, 1.62) on day 7. Conclusions: During the first week of orthodontic treatment, patients treated with Invisalign aligners reported lower pain than did those treated with passive self-ligating fixed appliances.