Hypocobalaminemia is a common complication in case of chronic diarrhoea in dogs. Reduced cobalamin (vitamin B12) causes diarrhoea, creating a viscous circle. A 10-year-old male intact Frisian pointing dog (18.9 kg; BCS 4/9) was presented to the primary care veterinarian diarrhoea. After 6 months of chronic diarrhoea with symptomatic treatments, lab analysis showed a reduction of cobalamin (145 pmol/L; reference 173- 599) and folic acid (18.5 nmol/L; reference 21.1-54.0). Consistent with hypocobalaminemia, a nonregenerative anaemia was found. Treatment consisted of weekly injections of 1 mg vitamin B12 (for 6 weeks) and the months of supplementation per os. Six months after the treatment, the discoloration was resolved. The mechanism of coat discoloration due to hypocobalaminemia is unclear, but multiple cases in humans are known. Vitamin B12 is supposed to influence melanin to impact the coat colour. To the authors’ knowledge, this is the first case in dogs of hypocobalaminemia resulting in coat discoloration.