Inhibition of myostatin activation with SRK-015 (apitegromab) is a promising muscle targeted approach for improving motor function in neuromuscular disorders. Apitegromab has demonstrated positive results in both preclinical models of Spinal Muscular Atrophy (SMA) and in a placebo-controlled phase III trial in SMA patients. Facioscapulohumeral muscular dystrophy (FSHD) is a neuromuscular disease in which sporadic DUX4 expression in myonuclei causes a patchy pattern of muscle fiber loss, with the unaffected motor units remaining intact. We hypothesized that selective myostatin inhibition with SRK-015 could improve muscle function in FSHD by enhancing these remaining motor units. We have studied the potential of SRK-015 in FSHD using the FLExDUX4.Cre mouse model, which recapitulates the patchy nature of muscle fiber loss and functional deficit observed in the disease. Treatment with SRK-015 drove improvements in muscle size, muscle function and running endurance in both male and female young FLExDUX4.Cre mice, as well as in aged mice. Positive effects with SRK-015 were also observed on muscle biomarkers and muscle cellular composition. These results support the continued investigation of apitegromab as an approach in FSHD.