Emerging evidence links dietary interventions to favorable multiple sclerosis (MS) outcomes; however, evidence for the efficacy of dietary interventions on functional disability remains sparse. Data from two 12-week, randomized, controlled pilot trials were pooled to investigate the efficacy of a modified Paleolithic diet (Paleo) on functional disability, as assessed by the MS Functional Composite (MSFC), among people diagnosed with MS. Pooled baseline-referenced MSFC scores were calculated from the nine-hole peg test (NHPT), timed 25-foot walk (T25FW), and Paced Auditory Serial Addition Test (PASAT) Z-scores. There was no significant difference in the mean change in MSFC scores between groups (p = 0.07). In the Paleo group, a significant increase was observed in the MSFC scores (p = 0.03), NHPT (p < 0.001), and PASAT (p = 0.04) Z-scores at 12 weeks, indicating reduced functional disability compared to baseline values. No significant changes were observed within the Control group. Study-specific differences in the MSFC changes between groups were observed. Functional disability was reduced compared to the baseline in the Paleo group, possibly depending on MS type. These results provide preliminary observations on the efficacy of a modified Paleolithic diet for reducing or maintaining functional disability in MS.