The glial cells missing (gcm) gene encodes an essential transcription factor that converts neuronal precursor cells to glial fate in the Drosophila nervous system. In this study, we tested effects of gcm ectopic expression on fate of non-neural cells. When gcm expression was continuously induced in epidermal cells from around stage 9, these cells started to exhibit mesenchymal cell morphology at stage 13, which was preceded by the onset of expression of Repo, a glial marker. The morphological change was coincident with loss of expression of an epidermal cell-adhesion molecule. In addition to the epidermis, fate of mesodermal cells was also affected by gcm ectopic expression. These findings suggest that gcm can convert gene expression and cell morphology even outside the neuroectoderm.