Cypermethrin is a synthetic pyrethroid insecticide used worldwide for domestic as well as agriculture purposes. The current research is designed to investigate the protective role of ashwagandha and quercetin on cypermethrin-induced hematological alteration via declined thyroid function. Swiss albino male mice weighing around 25–30 g were divided into four groups of six animals each at random. Group I served as a control with normal food and water; Group II cypermethrin treated 15 mg/kg body weight; Group III ashwagandha co-treated 200 mg/kg body weight, and Group IV quercetin co-treated 150 mg/kg body weight. Doses were applied orally for 28 days. Blood was drawn, and hematological parameters and a serum thyroid hormone calculation were performed on it. Increased body weight and decreased thyroid weight were observed in the cypermethrin exposure group. The decreased T3 and T4 and increased TSH hormone levels were observed in the cypermethrin-treated group as compared to the control signified hypothyroidism. A significant decrease in erythrocyte count, hemoglobin percentage, and platelet counts was observed in the cypermethrin exposure group. Total leukocyte counts, neutrophil%, and lymphocyte% were increased significantly in the cypermethrin exposure group as compared to the control. A significantly decreased platelet count was observed in the cypermethrin exposure group. The antioxidant co-administered animals showed significant prevention as compared to cypermethrin-exposed animals.