Epithelial cell motility is critical for self-rejuvenation of normal intestinal mucosa, wound repair, and cancer metastasis. This process is regulated by the reorganization of the F-actin cytoskeleton, which is driven by a myosin II motor. However, the role of myosin II in regulating epithelial cell migration remains poorly understood. This study addressed the role of non-muscle myosin (NM) IIA in two different modes of epithelial cell migration: two-dimensional (2-D) migration that occurs during wound closure and three-dimensional (3-D) migration through a Matrigel matrix that occurs during cancer metastasis. Pharmacological inhibition or siRNA-mediated knockdown of NM IIA in SK-CO15 human colonic epithelial cells resulted in decreased 2-D migration and increased 3-D invasion. The attenuated 2-D migration was associated with increased cell adhesiveness to collagen and laminin and enhanced expression of beta1-integrin and paxillin. On the 2-D surface, NM IIA-deficient SK-CO15 cells failed to assemble focal adhesions and F-actin stress fibers. In contrast, the enhanced invasion of NM IIA-depleted cells was dependent on Raf-ERK1/2 signaling pathway activation, enhanced calpain activity, and increased calpain-2 expression. Our findings suggest that NM IIA promotes 2-D epithelial cell migration but antagonizes 3-D invasion. These observations indicate multiple functions for NM IIA, which, along with the regulation of the F-actin cytoskeleton and cell-matrix adhesions, involve previously unrecognized control of intracellular signaling and protein expression.