Background: Ischemia-reperfusion (I/R) induced by testicular torsion can damage the testicles. In the present study, we assessed the effects of coenzyme Q10 (CoQ10) and diamond nanoparticles on sperm parameters in I/R testes in rats. Materials and Methods: Forty-eight Wistar adult male rats were divided into eight groups: healthy control (Ch), diamond nanoparticle healthy control group (Ch+Dia), CoQ10 healthy control group (Ch+Q10), diamond nanoparticles+CoQ10 healthy control group (Ch+Q10+Dia), torsion/detorsion group (Ct), the Ct group that received diamond nanoparticles (Ct+Dia), the Ct group that received CoQ10 (Ct+Q10), and Ct group that received diamond nanoparticles and CoQ10 (Ct+Q10+Dia). The rats were euthanized, and we collected the semen from the epididymal tissues to evaluate sperm viability, motility, concentration, and morphology parameters. Results: The I/R of the testicles significantly reduced sperm concentration, motility, viability, and altered sperm morphology in the rats. However, the administration of CoQ10 significantly improved sperm parameters in the rats with testicular I/R. Diamond nanoparticles decreased the sperm parameters; however, simultaneous administration of diamond nanoparticles and CoQ10 led to improved sperm parameters. Conclusion: CoQ10 potentially appeared to have protective effects against the long-term side-effects of I/R in testes in rats. Co-administration of diamond nanoparticles with CoQ10 significantly improved sperm parameters and greatly reduced the negative effects of diamond nanoparticles alone. Therefore, green synthesis of nanoparticles with the use of antioxidants such as CoQ10 is recommended. [GMJ.2021;10:e2029]