Understanding the seasonal epidemiology of diarrhoea, malaria and pneumonia relative to climatic factors is the thrust of the study. Empirical monthly data sets used covered the period of 2012M1-2019M12. Graphical exploration, methods of seasonal variability and Chi-square test of homogeneity were employed. The results showed that diarrhoea, malaria and Pneumonia are very high at the peak of rainy season (July-September) especially August, when humidity is relatively high and temperature is low. The result also indicted that the null hypothesis of no seasonal variation in the incidence of malaria and pneumonia is rejected in favour of the alternative as Chi-squared values are significant under 5% level respectively. This implies that the incidence of malaria and pneumonia have seasonal occurrence. However, the findings are imperative for the diseases seasonal determination, surveillance and control in Asaba, south-southern Nigeria.