Germline stem cells (GSCs), often called spermatogonial stem cells, are unipotent stem cells that can give rise only to gametes. Under defined culture conditions, unipotent GSCs can be converted into pluripotent stem cells, termed as germline-derived pluripotent stem (gPS) cells. gPS cells can be differentiated into cells forming all three germ layers and germ cells. In this study, we describe a simple and robust protocol for the derivation of GSCs from adult mouse testis and the rapid and reproducible conversion of GSCs into gPS cells. Under our defined culture conditions, GSCs can be converted into gPS cells in approximately 1 month. The initial number of plated GSCs and the culture time are two conditions that are critical for the successful conversion of GSCs into gPS cells. gPS cells are similar to embryonic stem cells, as judged by molecular and cellular properties and its development potential. Thus, generation of gPS cells holds potential for tissue regenerative medicine.