Background: Attention-deficit/hyperactivity disorder (ADHD) is a neurodevelopmental condition that originates in childhood and negatively affects functioning in several domains. According to recent research, the second-to-fourth digit ratio (2D:4D), representing the length of the index finger (2D) relative to the ring finger (4D), serves as a valid predictor of intrauterine testosterone levels due to its inverse correlation with prenatal testosterone exposure (PTE), remains stable throughout life. Objective: To study any possible relationship between 2D:4D, aggression and intelligence levels in children with ADHD. Patients and Methods: This was prospective randomized study, which was conducted on 60 children and adolescents diagnosed with ADHD at the Pediatric Neuropsychiatric Outpatient Clinic of Al-Azhar Assiut University Hospital during the period from 1^st of June 2021 to 31^st of March 2022. Results: The two groups under study differed statistically significantly in terms of age, sex, smoking exposure, sibling order, family history of chronic illness, and family history of ADHD. The two groups under study differed significantly in terms of Teacher T-DSM-IV-S, CPRS-RS, CTRS-RS, and Parent T-DSM-IV-S. The right and left hands of ADHD cases had lower 2D:4D compared to healthy control (p < 0.001). Conclusion: Compared to healthy controls, children with ADHD who have not received therapy had lower right-hand 2D:4D, which are a measure of PTE. Additionally, a potent inverse association between left-hand 2D:4D and hyperactivity ratings were seen. These findings offer more proof that the pathophysiology of ADHD could be affected by prenatal androgen exposure.