This chapter discusses structural and optical properties of novel GaNP nanowires (NW), as well as their potential for future applications in optoelectronics and photonics. It reviews efforts devoted to the optimization of GaNP-based NWs for future applications in light-emitting devices and discusses the impacts of structural polymorphism on the radiative efficiency and band structure of the material. The chapter shows that GaNP NWs can be utilized as a source of linearly polarized light with the polarization direction that is not determined by dielectric mismatch between the NW and its surrounding. GaNP alloys are novel III–V semiconductors, which have a great potential for applications in amber-red light-emitting diodes and also as an active material in innovative intermediate the band solar cells. NWs grown under the non-optimized conditions usually suffer from various point and structural defects, which degrade the radiative efficiency.