Myosins are important eukaryotic motor proteins that bind actin and utilize the energy of ATP hydrolysis to perform a broad range of functions such as muscle contraction, cell migration, cytokinesis, and intracellular trafficking. However, the characterization and function of is poorly studied in teleost fish. In this study, we identified 60 family genes in a marine teleost, black rockfish (), and further characterized their expression patterns. showed divergent expression patterns in adult tissues, indicating they are involved in different types and compositions of muscle fibers. Among 12 subfamilies, subfamily was significantly expanded, which was driven by tandem duplication events. The up-regulation of five representative genes of in the skeletal muscle during fast-growth stages of juvenile and adult revealed their active role in skeletal muscle fiber synthesis. Moreover, the expression regulation of during the process of myoblast differentiation suggested that they contribute to skeletal muscle growth by involvement of both myoblast proliferation and differentiation. Taken together, our work characterized genes systemically and demonstrated their diverse functions in a marine teleost species. This lays foundation for the further studies of muscle growth regulation and molecular mechanisms of indeterminate skeletal muscle growth of large teleost fishes.