Processing speed is a frequently affected cognitive domain in pediatric multiple sclerosis (MS) and is commonly assessed using the Symbol Digit Modalities Test (SDMT). The objective of this study was to determine maturational trajectories in SDMT performance and baseline factors affecting trajectories in a sample of 82 pediatric MS individuals. Performance on the SDMT increased with age in patients with pediatric MS followed by a subsequent decline. Furthermore, patients who were older at disease onset and had a higher IQ showed greater gains with age, suggesting that these factors may be protective with respect to cognitive maturation in pediatric MS.