The myosin heavy chain 9 (MYH9) gene encodes non-muscle myosin heavy chain IIA (NMIIA), a vital protein involved in fundamental cellular activities, including movement, cell division, and signal transmission. Mutations in MYH9 were initially linked to autosomal dominant disorders collectively termed MYH9-related diseases (MYH9-RD). In recent years, MYH9 has gained significant attention for its pivotal roles in various cancers. However, despite extensive research, its exact contributions to cancer progression remain incompletely understood. Targeting MYH9 through approaches such as non-coding RNAs, small molecules, or gene therapy presents a promising avenue for advancing cancer treatment. Additionally, the dual role of MYH9 in MYH9-RD and cancer raises the intriguing question: are individuals with MYH9 mutations predisposed to or protected from cancer? This review aims to present the structure, functional significance, and clinical associations of MYH9, with an emphasis on its contributions to MYH9-RD and cancer progression. Furthermore, it examines MYH9's regulatory interactions with non-coding RNAs and its potential applications as a therapeutic target, offering insights into strategies such as RNA interference and CRISPR-based gene editing for cancer treatment.