The aim of this study is to assess the agreement between orthodontist’s and Chinese young adult’s self-perceived aesthetics, the normative treatment need based on the Index of Orthodontic Treatment Need (IOTN), and the main factors affecting the self-perceived aesthetics. A random sample of 348 Chinese young adults (116 males and 232 females) aged 17–24 years were recruited in this study. Two orthodontists were involved in rating the cases. Orthodontic treatment need was assessed according to the Index of Orthodontic Treatment Need, including Aesthetic components and Dental Health Components (AC and DHC). Personality traits were assessed according to Eysenck Personality Questionnaire (EPQ). Cohen’s kappa test was used to assess the agreement, and spearman’s correlation coefficient was used to analyze the association among all variables. A statistically significant level of agreement was observed between young adult’s perception and orthodontist’s perception in IOTN (kappa = 0.14). A positive relationship (p < 0.001)existed between the young adult’s AC and the orthodontist’ s AC (r = 0.275), and between the young adult’ s AC and the normative need DHC (r = 0.195). The orthodontist’s AC was strongly related to the normative need (r = 0.743, p < 0.001). Association between the young adult’s AC and gender and EPQ-E were also observed. Young adults tend to be less critical in assessing orthodontic treatment needs than orthodontists. The orthodontist’s AC reflecting subjective treatment need is strongly connected to the normative need. The adult’s perception of aesthetic component is affected by factors such as gender and personality traits.