BACKGROUND Our objective was to assess the effect of different orthodontic treatment needs on the oral health-related quality of life of young adults. METHODS The study sample comprised 366 young adult orthodontic patients (153 men, 213 women; age range, 21-25 years). Each participant was assessed for orthodontic treatment need and oral health-related quality of life by using the dental health component of orthodontic treatment need index and the shortened version of oral health impact profile questionnaire. RESULTS Orthodontic patients who had little or no, borderline, and actual need for orthodontic treatment represented 14.8%, 56%, and 29.2% of the total sample, respectively. Orthodontic treatment need significantly affected mouth aching, self-consciousness, tension, embarrassment, irritability, and life satisfaction in both sexes. Also, orthodontic treatment need significantly affected taste and relaxation in both men and women. However, pronunciation and the ability to do jobs or function effectively were not significantly associated with orthodontic treatment needs in either sex. CONCLUSIONS These findings emphasize the impact of malocclusion on oral health-related quality of life of young adults.