Haematological analyses are important in early detection of diseases, and breed differences have been suggested (Schalm 1962). This work is a comparative study to establish the influence of breed on erythrocyte osmotic fragility of Nigerian indigenous breed of dog and the German shepherd dog. In the study, erythrocyte values and the erythrocyte osmotic fragility of Nigerian indigenous breed of dog were compared with those of the German shepherd dog. The influence of sex on the erythrocyte values of the German shepherd dog was also investigated. There were no significant differences (P<0.05) in the packed cell volume (PCV), haemoglobin (Hb) concentration, mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH) and mean corpuscular haemoglobin concentration (MCHC) between the two breeds. Red blood cell (RBC) count of the Nigerian indigenous breed of dog was significantly lower than that of the German shepherd dog (P<0.05). The study further reveals that there was no sex difference in the PCV, RBC count, Hb concentration, MCV, MCH and MCHC in the German shepherd dog. Also, erythrocytes of the Nigerian indigenous dog were more fragile than those of the German shepherd dog at 0.3 % NaCl concentration (P<0.05). Erythrocytes of male German shepherd dog were also observed to be more fragile than those of the female at 0.7 % NaCl concentration (P<0.05). This study forms part of an ongoing effort in establishing reference haematological values for the Nigerian indigenous breed of dog.