The canted G-type antiferromagnet PrFe_0.5Mn_0.5O_2.95 shows an enhanced Jahn-Teller (JT) distortion below 150K (T*). The resistivity of the grains can be described by variable range hopping between the localized states, and there is a dominant grain boundary contribution to dc resistivity, below T*. Above T*, the total dc resistivity follows small polaron hopping (SPH) conduction. A giant dielectric response is observed, and it can be ascribed to Maxwell-Wagner polarization and SPH mechanism. Despite the low concentration of JT active Mn³⁺ ions, our result indicates an important role of JT effect on physical properties of PrFe_0.5Mn_0.5O_2.95 .