Aim: The aim of this cohort study was to evaluate the perceptions of adolescents regarding pain levels and chewing impairment throughout the first 12 months of orthodontic treatment with fixed appliances. Methods: A total of 120 adolescents aged 11 and 12 years undergoing orthodontic treatment at the Faculty of Dentistry of the Federal University of Minas Gerais participated in this study. Malocclusion was evaluated by means of the Dental Aesthetic Index. Pain level and degree of chewing impairment were evaluated by means of two questions selected from the short form of the Child Perceptions Questionnaire (CPQ11-14). Each question had five response options with the following scoring system: never (0), once or twice (1), sometimes (2), often (3) and every day/almost every day (4). Both questions were answered by the adolescents at four different times: before fixed appliances’ placement (T1), one month after banding and fixed appliances’ bonding (T2), four months after banding and fixed appliances’ bonding (T3), and 12 months after banding and fixed appliances’ bonding (T4). Results: The mean age of adolescents was 11.39 (±0.68). Significant differences were observed for pain levels (p=0.038) and chewing impairment (p=0.020) over the study period. Pain levels at T1 were significantly lower than at T2 (p=0.038) and T4 (p=0.020). Chewing impairment at T1 was significant lower than at T2 (p<0.001), T3 (p=0.014) and T4 (p=0.005). Conclusion: Adolescents undergoing orthodontic treatment with fixed appliances present an increase in pain levels and in chewing impairment.