The Ages and Stages Questionnaires–3® (ASQ-3) for developmental screening in our young oncology patients was pilot tested in children 4 to 48 months of age with newly diagnosed cancer. Subjects were screened within 28 days of diagnosis (baseline), at 6 and 12 months. Twenty-six of 30 enrolled parents (87%) completed all 3 screens. Screens were completed by parents within 15 minutes. ASQ-3 screening identified unsuspected developmental delays as follows: 7 at baseline, 4 at 6 months, and 3 at 12 months. ASQ-3 developmental screening is feasible, identifies early developmental delays in young children with cancer, and helps initiate appropriate referrals.