To study the haematology of the German Shepherd breed of dog in a humid, tropical environment, an experiment was conducted to elucidate the effects of sex, age, and breed on the erythrocyte and leukocyte values of this species. There were no significant (p > 0.05) gender-related differences in the values of red blood cell counts (RBC), packed cell volume (PCV), haemoglobin (Hb) concentration, mean corpuscular haemoglobin concentration (MCHC), mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH), total and differential white blood cell counts (WBC) of the German Shepherd dog. The study also revealed that the adult German Shepherd dog (between 3 and 5 years old) had significantly higher RBC, total WBC, PCV and Hb, MCV, MCH, MCHC and lymphocyte values than a younger animal (between 8 and 15 weeks old). However, neutrophil, monocyte and eosinophil counts were similar (p > 0.05) in the two age groups. Although there were no breed differences in the erythrocyte values between the Nigerian local dog and the German Shepherd dog, the WBC and neutrophil counts were however significantly higher in the Nigerian dog. This study revealed that although there were no gender or breed differences in the erythrocyte values of the German Shepherd dog, there were some age-related differences.