Patients with a fixed orthodontic appliance may have difficulties in maintaining good oral health-related quality of life (OHRQoL), and evaluating self-perceived OHRQoL in orthodontic patients could be challenging for their orthodontists. Therefore, this research was conducted to investigate whether orthodontic postgraduates would accurately evaluate the OHRQoL of their patients. Two self-administered questionnaires were designed for patients to rate their OHRQoL and for their orthodontic postgraduates to evaluate them on OHRQoL. All pairs of patients and their orthodontic postgraduates were requested to independently complete the questionnaires. Pearson’s correlation and multiple linear regression were performed to determine the relationships of the variables and to identify significant predictors on OHRQoL, respectively. There were 132 pairs of orthodontic patients and their residents who completed the questionnaires. There were no significant correlations between OHRQoL perceived by patients and evaluated by their orthodontic postgraduates in all aspects of treatment needs and dietary difficulties (p > 0.05). In addition, the regression model demonstrated no significant predictors for the self-perceived treatment needs and dietary difficulties of orthodontic patients. There seemed to be challenges for orthodontic postgraduates to evaluate their patients’ oral health-related quality of life. Therefore, the OHRQoL measures should be increasingly implemented in orthodontic education and practice in order to enhance the concept of patient-centered care.