Cryopreservation has adversely effects on sperm function and structure, while the nanotechnology can be used to optimize this process. Thereafter, this research aimed to investigate the effects of adding spirulina platensis nanoparticles (SPNP) or selenium-coated spirulina nanoparticles (SPSE) to a freezing extender on the quality of post-thawed bull sperm and anti-oxidant related markers. Five healthy proven-fertile bulls were used for semen collection using an artificial vagina. The semen samples were divided into three groups: the first one was extended without supplementation (CON), the second group was supplemented with spirulina nanoparticles (SPNP; 10 μg/mL), and the third group was supplemented with selenium (0.5 μg/mL) coated spirulina nanoparticles (SPSE; 10 μg/mL). Compared to the CON group, the supplemented groups showed significant improvements in the percentages of progressive motility, livability, and plasma membrane integrity (P<0.05). Additionally, the percentages of sperm abnormalities and chromatin damage were significantly decreased in the supplemented groups. The SPSE group had the highest activity of total antioxidant capacity (P<0.001). All supplemented groups significantly improved superoxide dismutase (P<0.001), the viable sperm, but significantly reduced the malondialdehyde levels and the apoptotic sperm. The addition of SPNP or SPSE sustained the sperm bull ultrastructure (plasma membrane, acrosome integrity, and normal mitochondrial). In conclusion, the results indicate that adding SPNP or SPSE to the freezing extender significantly improves the quality of post-thawed bull sperm by enhancing antioxidant biomarkers, reducing lipid peroxidation, and maintaining sperm ultrastructure.