The non-muscle myosin IIA (NM IIA), encoded by non-muscle myosin heavy chain 9 (MYH9), is a member of the non-muscle myosin II family. NM IIA is expressed in a variety of cell types and plays a critical role in cellular physiological processes, such as cell contraction, cell migration, and cell shape maintenance. NM IIA is essential for the development of the brain, kidney, vessels, and other organs. A mutation of NM IIA causes MYH9-related disease (MYH9-RD). Recently, it has been shown that NM IIA is also involved in the regulation of other physiological and pathological processes, such as angiogenesis and tumor progression. Here, we summarize the recent progress of research on NM IIA functions in humans, mice, and zebrafish.