Objective: ADHD youth show poor oculomotor control. Recent research shows that attention-related eye vergence is weak in ADHD children. Method: To validate vergence as a marker to classify ADHD, we assessed the modulation in the angle of vergence of children ( n = 43) previously diagnosed with ADHD while performing an attention task and compared the results with age-matched clinical controls ( n = 19) and healthy peers ( n = 30). Results: We observed strong vergence responses in healthy participants and weak vergence in the clinical controls. ADHD children showed no significant vergence responses. Machine-learning models classified ADHD patients ( n = 21) from healthy controls ( n = 21) with an accuracy of 96.3% (false positive [FP]: 5.12%; false negative [FN]: 0%; area under the curve [AUC]: 0.99) and ADHD children ( n = 11) from clinical controls ( n = 14) with an accuracy of 85.7% (FP: 4.5%; FN: 19.2%, AUC: 0.90). Conclusion: In combination with an attention task, vergence responses can be used as an objective marker to detect ADHD in children.