Purpose: The goal of this study was to compare the effect of early corneal collagen cross-linking (CXL) intervention (before 17 years of age) with that of late intervention (after 17 years of age) on the characteristics and progression of keratoconus. Patients and Methods: One hundred five eyes of 94 patients with keratoconus undergoing treatment with CXL were included. The patients were divided into 2 groups by age: group 1 (mean age of 13.8 yrs; range 10-16) and group 2 (mean age of 21.5 yrs; range 17-36). Eyes were evaluated regarding best-corrected visual acuity (BCVA), refractive error, corneal endothelial cell density, and central corneal thickness, as well as using slit-lamp biomicroscopy, Goldmann tonometry, and the keratometry (Kmax, Ksteep, and Kflat parameters) test before CXL and at 1, 3, 6, and 12 months thereafter. Results: The mean (SD) BCVA of group 1 was 0.45 (+/- 0.25) before CXL and 0.56 (+/- 0.29) 1 year after CXL (P = 0.030); mean (SD) Kmax, Ksteep, and Kflat were 58.47 (+/- 7.2), 52.93 (+/- 5.4), 47.22 (+/- 4.2) before CXL respectively, and 58.21 (+/- 7.7), 52.25 (+/- 5.5), and 46.56 (+/- 4.6) 1 year after CXL, respectively (P = 0.897, 0.481, and 0.491). The mean (SD) BCVA of group 2 was 0.50 (+/- 0.30) before CXL and 0.56 (+/- 0.32) 1 year thereafter (P = 0.346); mean (SD) Kmax, Ksteep, and Kflat were, respectively, 57.64 (+/- 7.1), 54.02 (+/- 6.2), and 48.60 (+/- 4.1) before CXL and 56.46 (+/- 8.0), 52.46 (+/- 5.8), and 47.85 (+/- 4.9) 1 year after CXL, respectively (P = 0.553, 0.258, and 0.640). Conclusions: The study showed no statistical differences between younger and older patients. These findings support the indication of CXL treatment in pediatric patients for early stabilization of the disease and better progress regarding BCVA and keratometry parameters.