Updated project metadata. Mechanical forces regulate cell behavior and tissue morphogenesis. In particular, cardiac tissues require mechanical stimuli generated by the heartbeat for differentiation and maturation, but the molecular mechanisms underlying these processes remain unclear. Here, we first show that mechanical forces acting via the mechanosensitive factor Vinculin (VCL) are essential for cardiomyocyte myofilament maturation and that cardiac contractility regulates the localization and activation of Vinculin. To further analyze the role of Vinculin in myofilament maturation, we examined its interactome in contracting cardiomyocytes and found many cytoskeletal factors including actinins. We also identified Slingshot protein phosphatase 1 (SSH1), which we show is recruited by Vinculin to regulate F-actin rearrangement and myofilament maturation through its association with the actin depolymerizing factor Cofilin (CFL). Together, our results reveal that mechanical forces generated by cardiac contractility regulate cardiomyocyte maturation through the VCL-SSH1-CFL axis, providing mechanistic insight into how mechanical forces are transmitted intracellularly to regulate myofilament maturation.