Pluripotent or multipotent stem cells are involved in development and tissue homeostasis; they have the ability to self-renew and differentiate into various types of functional cells. To maintain these properties, stem cells must undergo sustained or unlimited proliferation that requires the stabilization of telomeres, which are essential for chromosome end protection. Telomerase, an RNA-dependent DNA polymerase, synthesizes telomeric DNA. Through the lengthening of telomeres the lifespans of cells are extended, or indefinite proliferation is conferred; this is intimately associated with stem cell phenotype. This review highlights our current understanding of telomerase as a "stemness" enzyme and discusses the underlying implications.