Objective: Sleep deprivation in adolescents has lately become a health issue that tends to increase with higher stress prevalence, extenuating routines, and new technological devices that impair adolescents’ bedtime. Therefore, this study aimed to assess the excessive sleepiness frequency and the factors that might be associated to it in this population. Methods: The cross‐sectional study analyzed 531 adolescents aged 10–18 years old from two private schools and one public school. Five questionnaires were applied: the Cleveland Adolescent Sleepiness Questionnaire; the Sleep Disturbance Scale for Children; the Brazilian Economic Classification Criteria; the General Health and Sexual Maturation Questionnaire; and the Physical Activity Questionnaire. The statistical analyses were based on comparisons between schools and sleepiness and non‐sleepiness groups, using linear correlation and logistic regression. Results: Sleep deprivation was present in 39% of the adolescents; sleep deficit was higher in private school adolescents (p < 0.001), and there was a positive correlation between age and sleep deficit (p < 0.001; r = 0.337). Logistic regression showed that older age (p = 0.002; PR: 1.21 [CI: 1.07–1.36]) and higher score level for sleep hyperhidrosis in the sleep disturbance scale (p = 0.02; PR: 1.16 [CI: 1.02–1.32]) were risk factors for worse degree of sleepiness. Conclusions: Sleep deficit appears to be a reality among adolescents; the results suggest a higher prevalence in students from private schools. Sleep deprivation is associated with older age in adolescents and possible presence of sleep disorders, such as sleep hyperhidrosis.