Background: The World Health Organization is saddled with the responsibilities of regulating health care services across the globe and had over the years provided reference values to various medical parameters for clinicians and medical research. However, due to socio-economic variations amidst different populations in various parts of the world, the standard reference values had significantly differed among different races, tribes, gender and socio-economic backgrounds. Consequently, several regions of the world now had their respective local medical references. Back home in Nigeria and Port Harcourt in particular, over-reliance on this WHO references still prevail as a result of the absence of our local reference data. To this end, this study therefore investigates the Effect of Socioeconomic Status on Haematological Indices in Port Harcourt Nigeria. Materials and Methods: A total of 112 participants across 3 different socio-economic classes (Upper, Middle and Lower Classes) were recruited into the study using well-structured questionnaires based on purposive non-probability sampling techniques. Blood samples were also aspirated and analysed for haematological parameters (Hb, PCV, RBC, WBC, Platelets) against their socio-economic variables (gender, level education, income level and nutritional intakes). Results and Discussions: Result from the study showed that both male and female haematological parameters were significantly (ρ≤0.05) different from the WHO reference. Significant difference in low and high level education was also noted among the educational group whereas the middle class education was not. The income level among the 3 economic classes and their nutritional groups were also significant (ρ≤0.05) whereas those on balanced diets were not. Conclusion: The study therefore concluded that gender, income, education and nutrition of the people of Port Harcourt significantly (ρ≤0.05) affected their haematological parameters as compared with the global .....