Most vertebrates have two nasal epithelia: the olfactory epithelium (OE) and the vomeronasal epithelium (VNE). The apical surfaces of OE and VNE are covered with cilia and microvilli, respectively. In rodents, signal transduction pathways involve Gα_olf and Gα_i2/Gα_o in OE and VNE, respectively. Reeve's turtles (Geoclemys reevesii) live in a semiaquatic environment. The aim of this study was to investigate the localization of G proteins and the morphological characteristics of OE and VNE in Reeve's turtle. In-situ hybridization analysis revealed that both Gα_olf and Gα_o are expressed in olfactory receptor neurons (ORNs) and vomeronasal receptor neurons (VRNs). Immunocytochemistry of Gα_olf/s and Gα_o revealed that these two G proteins were located at the apical surface, cell bodies, and axon bundles in ORNs and VRNs. Electron microscopic analysis revealed that ORNs had both cilia and microvilli on the apical surface of the same neuron, whereas VRNs had only microvilli. Moreover Gα_olf/s was located on only the cilia of OE, whereas Gα_o was not located on cilia but on microvilli. Both Gα_olf/s and Gα_o were located on microvilli of VNE. These results imply that, in Reeve's turtle, both Gα_olf/s and Gα_o function as signal transduction molecules for chemoreception in ORNs and VRNs.