The medial hypothalamus in tilapia, a percomorph teleost, receives ascending fibers from the primary and secondary general visceral sensory nuclei in the brain stem. However, fiber connections of the medial hypothalamus have remained to be revealed in detail. In the present study, we investigated fiber connections of the medial hypothalamus in tilapia Oreochromis niloticus by means of tract-tracing methods with biotinylated dextran amine (BDA), focusing on ascending connections to the telencephalon. Injections of BDA into the medial hypothalamus resulted in labeled terminals in a total of nine telencephalic structures: anterior parvocellular, posterior parvocellular and magnocellular preoptic nuclei, ventral (Vv), dorsal (Vd), and supracommissural (Vs) parts of the ventral telencephalic area, and parvocellular portion of lateral part (pDl), medial portion of rostral region of central part (rDcm), and parvocellular rostral portion of medial part (prDm) of the dorsal telencephalic area. Labeled somata were found in the same forebrain structures where labeled terminals were detected, except the magnocellular preoptic nucleus. Labeled terminals were also found in five diencephalic nuclei. Injections of BDA into the Vs, Vv, and a region of the rDcm plus prDm resulted in labeled somata and terminals in the medial hypothalamus, whereas injections into the Vd and pDl resulted in labeled terminals in the medial hypothalamus. Also, we found that the Vv, Vd, and Vs were reciprocally connected with the olfactory bulb. As the medial hypothalamus receives ascending fibers from the primary and secondly general visceral sensory nuclei in the brain stem, the present study suggests that the medial hypothalamus of teleosts integrates general visceral and olfactory information and sends outputs to the ventral telencephalic area and rostral zone of dorsal telencephalic area.