Follicular dysplasia is a rare skin disease of dogs characterized by abnormal hair regrowth and consequent alopecia. An 8-year-old female neutered Thai Bangkaew is presented with a history of hair loss since 6 years of age without pruritus or inflammation, marked hyperpigmentation on the trunk, peripheral limbs and tail. The differential diagnosis included hormonal diseases, follicular dysplasia and immune-mediated alopecia. Total T4 and blood chemistry were normal in results. Skin biopsy revealed epidermal and follicular hyperkeratosis, melanin clumping in hair bulbs, dysplastic hair shafts and follicles. Melatonin at the dosage of 6 mg/dog twice daily and niacinamide at the dosage of 500 mg/dog once daily were given for 8 weeks. Skin appearance was very improved with new hair regrowth in normal color and marked reduction of the black skin. In conclusion, the combination therapy of melatonin and niacinamide is effective for follicular dysplasia without adverse effect. The owner was satisfied with this treatment. Additionally, oatmeal shampoo and skin moisturizers can help to alleviate the dog's discomfort from this disorder.