Strain is the inherent phenomenon that occurs during the synthesis and fabrication of low-dimensional materials and significantly affects the material properties. Thus, it needs to be addressed to better understand two- and one-dimensional materials. In this work, we systematically investigate the strain effect on the electronic and magnetic properties of oxygen- and sulfur-passivated zigzag GaN nanoribbons (Z-GaNNRs) using first-principles density-functional theory. Our findings indicate that oxygen-passivated NRs (O-Z-GaNNRs) are more stable than the sulfur-passivated NRs (S-Z-GaNNRs). Our study reveals that, under strain-free conditions, the magnetic behaviors and electronic structure of GaNNRs as well as Ga–N bond lengths depend on passivating elements, while compressive and tensile strain leads to drastic changes in the electronic structure and material nature of bare as well as passivated Z-GaNNRs. Specifically, under −4% compressive strain, the half-metallic nature of bare Z-GaNNRs transforms into a semiconductor. O-Z-GaNNRs start to exhibit metallic nature under −4% and −6% strains, while AFM to FM transition occurs at the same compressive strains, whereas the magnetic properties of S-Z-GaNNRs remain unchanged. These results advance the understanding of these unique properties of GaNNRs and open a path for the development of magnetic one-dimensional nanomaterials for use in nanospintronic devices and pressure nanosensors.