The study was aimed to explore the role of auto antibodies against thyroperoxidase (TPO) as a causative factor of primary hypothyroidism in dogs. Dogs presented at Referral Veterinary Polyclinic, Indian Veterinary Research Institute during 2016-17, were screened for hypothyroidism on the basis of clinical signs like lethargy, thickening of skin, bilateral symmetrical alopecia and obesity. Serum and blood samples were collected for biochemical parameters, thyroid profile, TPO concentration and complete blood count. Twenty (20) dogs found positive for hypothyroidism during the study period. Adult dogs aged more than 5 years were commonly affected. Male and female dogs were equally susceptible to hypothyroidism and there was no sexual susceptibility. Clinical pathology revealed significant reduction in FT4 level, altered protein, cholesterol and lipid metabolism in affected dogs. Thyroperoxidase ELISA study showed negligible role of auto-antibodies against TPO as a causative factor of primary hypothyroidism in dogs. All the affected dogs were treated with L-thyroxine (Eltroxin)® @ 20 – 40 mcg/kg bid for life long period along with other symptomatic therapy.