Zn3As2 is an important p-type semiconductor with the merit of high effective mobility. The synthesis of single-crystalline Zn3As2 nanowires (NWs) via a simple chemical vapor deposition method is reported. High-performance single Zn3As2 NW field-effect transistors (FETs) on rigid SiO2/Si substrates and visible-light photodetectors on rigid and flexible substrates are fabricated and studied. As-fabricated single-NW FETs exhibit typical p-type transistor characteristics with the features of high mobility (305.5 cm2 V−1 s−1) and a high Ion/Ioff ratio (105). Single-NW photodetectors on SiO2/Si substrate show good sensitivity to visible light. Using the contact printing process, large-scale ordered Zn3As2 NW arrays are successfully assembled on SiO2/Si substrate to prepare NW thin-film transistors and photodetectors. The NW-array photodetectors on rigid SiO2/Si substrate and flexible PET substrate exhibit enhanced optoelectronic performance compared with the single-NW devices. The results reveal that the p-type Zn3As2 NWs have important applications in future electronic and optoelectronic devices.