This study proposes the use of a ZnO-nanowire (ZnO-NW)-based heterojunction structure for applications of nano optoelectronic sensors and photovoltaic devices. Nano heterojunctions (NHJs) were formed via e-beam deposition of p-type nickel oxide (NiO) onto the vertical-aligned ZnO-NWs grown by hydro-thermal growth method. The dark J-V curve shows that the prepared NiO/ZnO-NWs NHJ has a diode-like behavior with a forward threshold voltage (Vth) of 1.2 V and a leakage current (Jr at -1V) of 0.02 μA/cm2, respectively. It also exhibits a superior response to UV (366 nm) and AM 1.5G light illuminations. The Vth and the photocurrents (i.e., J r at -1V) under UV (366 nm @ 6 mW/cm2) and AM 1.5G light were 0.7 V/0.06 μA/cm2 and 0.5 V/ 3.2 μA/cm2, respectively, revealing an increase in the diode current of about 3x and 160x, respectively.