<p>Adverse childhood experiences (ACEs) are increasingly being recognized as an important risk factor for attention-deficit/hyperactivity disorder (ADHD). However, their relationship has not been adequately explored in low- and middle-income countries, including India. This study aims to explore the association between ACEs and ADHD symptoms among young adults in Delhi-NCR, India. This cross-sectional study included 1646 young adults aged 18–25 years. Sociodemographic data were collected using a pretested and modified interview schedule. ACEs were recorded using the ACE-International Questionnaire, and ADHD symptoms were screened using the ASRS v1.1 tool. Overall, the ACE-exposed group was 1.8 times more likely to have ADHD symptoms than the unexposed group [OR (95% CI) = 1.801 (1.240–2.615), <i>p</i> = 0.002]. Regarding ADHD subtypes, ACE exposure posed a 1.7-fold increased risk of inattentive type ADHD (ADHD-I) [OR (95% CI) = 1.779 (1.107–2.859), <i>p</i> = 0.017]. Further, the study also revealed a dose-response increase in the risk of overall ADHD symptoms and their subtypes with increasing ACE levels. Exposures to individual ACE domains, including household substance use, household mental illness, incarcerated household member, household violence, emotional neglect, any type of abuse, and bullying, were associated with higher odds of overall ADHD symptoms, but the associations varied across ADHD subtypes. These findings underscore the importance of ACEs in ADHD epidemiology in India and similar settings, where ACEs are often under-recognized as significant determinants of health. Prioritizing ACE screening in paediatric and adolescent populations may facilitate early identification of ADHD risk. Further, an ACE-informed approach may support the management of adult ADHD symptoms.</p>