Improving human regeneration has the potential to increase health span as a broad approach that seeks to repair or replace rather than treat damaged tissue. One of the fundamental requirements of regeneration is cellular proliferation. Understanding how proliferation must be regulated by extrinsic and intrinsic factors during regeneration will be key to developing therapies that promote tissue regeneration in humans. Extracellular vesicles (EVs) are secreted nanoparticles that carry signaling cargo, enabling cells to communicate with each other and coordinate numerous processes including proliferation. EVs have steadily gained attention in the field of regenerative medicine because of their ability to influence stem, progenitor, and mature cell behaviors during tissue repair. Similarly, tissue injury upregulates proliferation, often by modulating the cell cycle. Therefore, the intrinsic control of the cell cycle in stem and progenitor cells is intimately linked to the balance between proliferation and differentiation, ensuring the appropriate response to tissue loss. In particular, cytokinetic abscission at the end of mitosis is not only required for production of two functional daughter cells, but is also a key regulation point that influences division symmetry and fate. How and whether animals with greater regenerative capacity coordinate EVs and cytokinesis to regenerate after an injury is not clear. In this dissertation, I investigated the role of EVs and cytokinesis in Schmidtea mediterranea, a planarian flatworm with exceptional regenerative abilities driven by pluripotent stem cells called neoblasts. I found that planarians produced EVs that were taken up by neoblasts. EVs from regenerating planarians promoted proliferation when injected into live animals. The ortholog of ALG-2 interacting protein X (ALIX), a cytokinesis and EV biogenesis regulator in mammals, was required for regeneration and neoblast maintenance. ALIX inhibition caused the accumulation of cells with DNA content over 4N, similar to inhibition of Pavarotti, another cytokinesis regulator. In addition, ALIX inhibition 12 modulated EV biogenesis and pro-proliferative activity. Together, my work implicates EVs and conserved cytokinesis regulators in the coordination of planarian stem cell proliferation. These investigations set the stage to elucidate mechanisms by which EVs and cytokinesis control proliferation and differentiation during regeneration in vivo.