Adult intestinal tissues, exposed to the external environment, play important roles including barrier and nutrient-absorption functions. These functions are ensured by adequately controlled rapid-cell metabolism. GATA transcription factors play essential roles in the development and maintenance of adult intestinal tissues both in vertebrates and invertebrates. We investigated the roles of GATAe, the Drosophila intestinal GATA factor, in adult midgut homeostasis with its first-generated knock-out mutant as well as cell type-specific RNAi and overexpression experiments. Our results indicate that GATAe is essential for proliferation and maintenance of intestinal stem cells (ISCs). Also, GATAe is involved in the differentiation of enterocyte (EC) and enteroendocrine (ee) cells in both Notch (N)-dependent and -independent manner. The results also indicate that GATAe has pivotal roles in maintaining normal epithelial homeostasis of the Drosophila adult midgut through interaction of N signaling. Since recent reports showed that mammalian GATA-6 regulates normal and cancer stem cells in the adult intestinal tract, our data also provide information on the evolutionally conserved roles of GATA factors in stem-cell regulation.