Abstract: Characteristic variation of relative humidity and solar radiation enhances the understanding of the significance of indicated trends of variability to everyday life and the factors that might be responsible for such variations. This study critically analyses the seasonal trends and the existing relationship between solar radiation and relative humidity of Ibadan, Nigeria. The data used for the study were extracted from a 48 months (1999-2001) daily radiation data estimated from Gunn-Bellani distillate and relative humidity obtained from International Institute for Tropical Agriculture (IITA) Ibadan (7.3�N, 3.3�E), Oyo State. Simple graphical methods were adopted to analyze the trends of variation, using average monthly values for each parameter. The monsoon depression usually occurs annually during the month of August. The minimum value of solar radiation and a high value of relative humidity of 10.3MJ/m2/day and 87.8%, respectively were recorded during this month. The curves on the mean relative humidity are inversely proportional to observed curves on solar radiations.