Collective cell migration underlies many biol. processes, including embryonic development, wound healing, and cancer progression. In the embryo, cells have been observed to move collectively in vortices using a mode of collective migration known as coherent angular motion (CAM). Here, to determine how CAM arises within a population and changes over time, we studied the motion of mammary epithelial cells within engineered monolayers, in which the cells moved collectively about a central axis in the tissue. Using quant. image anal., we found that CAM was significantly reduced when mitosis is suppressed. Particle-based simulations recreated the observed trends, suggesting that cell divisions drive the robust emergence of CAM and facilitate switches in the direction of collective rotation. Our simulations predicted that the location of a dividing cell, rather than the orientation of the division axis, facilitates the onset of this motion. These predictions agreed with exptl. observations, thereby providing, to our knowledge, new insight into how cell divisions influence CAM within a tissue. Overall, these findings highlighted the dynamic nature of CAM and suggested that regulating cell division is crucial for tuning emergent collective migratory behaviors, such as vortical motions observed in vivo.