In this study, we used a simple green method for preparing tellurium nanoparticles and mainly evaluated their toxicological effects. The nanoparticles were synthesized using lactose and characterized with different instrumentation methods. The in vitro and in vivo cytotoxicity of tellurium nanoparticles and its effect on lipid profile were also evaluated. Hydroxyl-capped tellurium nanoparticles were successfully fabricated by lactose. The results showed spherical tellurium nanoparticles with a mean size of 89 nm. The toxicological study showed that the tellurium nanoparticles did not exhibit any toxicity on the primary cells. The LD50 values for the nanoparticles were 327 and 295 mg/kg for oral and intraperitoneal administrations, respectively. Also, the results showed a significant reduction in liver enzymes at the 16, 24, and 40 mg/kg doses. Hematological parameters indicated no significant suppressive changes between the animals that were administered tellurium nanoparticles and the control group. In addition, the effects of tellurium nanoparticles on hypercholesterolemic risk factors in mice fed with cholesterol demonstrated the depletion of triglyceride, cholesterol, and low-density lipoprotein. This study showed that the toxicity of tellurium nanoparticles was lower than tellurium ions. Furthermore, tellurium nanoparticles decreased the cholesterol and triglyceride levels in the animal model.