Abstract In this era, various traditional medicinal herbs were researched for their toxicological and safety aspects. The present study focused on using Nigella sativa fixed (NSFO) and essential oil (NSEO) to mitigate the adverse consequences of oxidative stress. For the purpose, oxidative stress was induced in Sprague Dawley rats using potassium bromate injection. The effect of NSFO and NSEO on indices of serum chemistry and hematology were studied. The results indicated that potassium bromate imparted drastic changes in serum chemistry and hematology e.g. it increased the blood cholesterol and blood glucose along with decreasing the insulin secretion. Oxidative stress also influenced the hematological attributes negatively but experimental diets were slightly successful in normalizing the values. The experimental diets especially essential oil that contains significant quantities of thymoquinone modulated the adverse consequences of oxidative stress with special reference to hematology and serological attributes. In the nutshell, NSFO and NSEO hold potential to mitigate the oxidative stress, and improved various serological and hematological attributes.