There is a critical need for additional validation studies of questionnaires designed to assess the level of control of asthma in pediatric patients.To validate the Spanish version of the Childhood Asthma Control Test (cACT) in children aged between 4 and 11 years with physician-diagnosed asthma.In a prospective cohort validation study, asthmatic children aged between 4 and 11 years and their parents, attended both a baseline and a follow-up visit 2 to 6 weeks later. In these two visits, they completed the information required to assess the criterion validity, construct validity, test-retest reliability, sensitivity to change, internal consistency and usability of the cACT.At baseline, cACT scores were significantly different between patients with controlled, partly controlled and uncontrolled asthma [24.0 (23.0-26.0), 18.0 (18.0-22.0), and 17.5 (13.0-20.0), respectively, p < 0.001], and also between patients for whom this visit resulted in a step-up, no change or step-down in therapy [18.0 (15.0-21.0), 24.0 (23.0-24.0) and 26.0 (23.5-26.0) respectively, p < 0.001]. The score of the cACT correlated positively and significantly with the score of the Pediatric Asthma Caregivers Quality of life Questionnaire--PACQLQ (Spearman's rho = 0.50, p < 0.001). The intraclass correlation coefficient of the measurements in patients with no change in clinical status was 0.849 (95% CI: 0.752-0.908). There were statistical significant differences between baseline and follow-up cACT scores in patients with an improvement in clinical status [19.0 (18.0-22.0) versus 24.5 (24.0-25.0), p < 0.001]. Cronbach's α was 0.8276 for the questionnaire as a whole.The Spanish version of the cACT has adequate criterion validity, adequate construct validity, adequate sensitivity to change, good internal consistency, good test-retest reliability and excellent usability when administered to asthmatic children aged between 4 and 11 years.