A two-year-old, intact male, 45 kg Doberman Pinscher was referred with dermal nodular lesions affecting the left hindlimb. The cytological examination revealed eosinophilic inflammation. Skin biopsy specimens showed canine eosinophilic granuloma (CEG). The dog was administered oral prednisolone (1.5 mg/kg/day) and azathioprine (2 mg/kg/day). After one week, the skin lesions diminished dramatically, but the dog presented with severe watery diarrhea. The prednisolone dose was reduced by 0.9 mg/kg/day. The lesions and diarrhea improved markedly after one week. Prednisolone was tapered by 25% of the previous dose every week to 0.2 mg/kg/day. Azathioprine was also reduced to therapy every other day. After seven weeks of combination treatment, the medications were withdrawn, but the dog had a recurrence one week later. Azathioprine (2 mg/kg/EOD) was reintroduced for two weeks. There was no relapse after all the medications had been withdrawn. This case indicates that CEG can be managed with prednisolone and azathioprine. Azathioprine may be an effective adjunctive immunosuppressive agent, and may be considered as a well-tolerated prednisolone sparing agent to treat CEG.