Knowledge of densities of rocks is essential in petrological and geological studies, interpretation of gravity anomalies and ground water exploration. Fifty samples were collected from Abeokuta, Sagamu, Odeda, Ewekoro, Ibese Yewa North Local Government, Ijebu East Local Government and Obafemi Owode in Ogun State and dry bulk density, saturated density, porosity and particle density were determined. Results showed that Ewekoro shale has the lowest mean density of 1.35 g/cm3 while Ibese, Yewa North Local Government limestone has the highest mean density of 3.9 g/cm3. Porosity ranges from 0.030 to 0.640 with the granite in Odeda local government having the highest porosity and the shale in Ewekoro local government having the lowest porosity. Mean porosity for all the rocks samples in the seven Local Government Areas was 0.34. Test of significance revealed that there is significant relationship in the values of density of rock samples within the state.