The aim of this study was to investigate the effect of orthodontic treatment on the maxillofacial growth of patients with unilateral cleft lip and palate. The Great Ormond Street, London and Oslo (GOSLON) yardstick was used for a longitudinal evaluation of 24 patients with cleft lip and palate treated at the Cleft Center of the Lauro Wanderley University Hospital, Paraiba State, northeastern Brazil. Dental casts were evaluated by 3 orthodontists and classified according to the GOSLON yardstick. The evaluation was performed at 2 different stages: T1 (before orthodontic treatment) and T2 (follow-up evaluation) after a 6-year mean follow-up interval. The Kappa test was used to evaluate intra- and interexaminer agreement, and paired t-test was used to compare the differences between T1 and T2, with a 99% confidence interval. The average intraexaminer Kappa was 0.979, ranging from 0.971 to 0.990. The interexaminer Kappa value was 0.926 at T1, ranging from 0.885 to 0.964, and 0.896 at T2, ranging from 0.696 to 1.0. The mean GOSLON yardstick found at T1 was 2.5 ± 1.18 with 50% in G1 + G2, 29.18% in G3, and 20.82% in G4 + G5. At T2, the GOSLON average was 1.71 ± 1.12, with 79.18% in G1 + G2, 12.5% in G3, and 8.32% in G4 + G5. A statistically significant difference was found between T1 and T2. The results suggest that orthodontic treatment improves facial growth in patients with unilateral cleft lip and palate.