Sleep problems are highly prevalent in patients with attention-deficit/hyperactivity disorder (ADHD). Although chronotype has been linked to behavioral problems, its specific contribution to ADHD symptoms remains unclear. We assessed the association between chronotype and sleep and behavioral problems in adolescents with ADHD between 12 and 18 years of age using questionnaires (Morningness–Eveningness Scale for Children [MESC], Strengths and Difficulties Questionnaire [SDQ], and Pediatric Sleep Questionnaire [PSQ]). Overall, 84 families (parents and adolescents) were enrolled. The intermediate chronotype was the most common in the study sample. No sex differences were detected in the proportion of morning, intermediate, and evening types. No correlation was found between MESC score and body mass index nor total PSQ score. Regarding SDQ, a significant negative correlation was found between the MESC score and hyperactivity/inattention score. We conclude that adolescents with ADHD tend to have an intermediate chronotype and eveningness is related to hyperactivity/inattention problems.