Background: The annual effective dose equivalent (AEDE) due to ionizing radiation in a coaster area in Nigerian has been determined using Geiger-Muller counter. Materials and Methods: isolevels in the study area were represented by using the kriging interpolation technique on ArcGIS 10.1 software. Duncan multiple range test was performed using Statistical Package for Social Sciences (SPSS). Results: The results obtained show that the AEDE ranged from 0.19±0.01 to 0.35±0.02 mSv y^-1 with a mean of 0.27±0.03 mSv y^-1. The excess lifetime cancer risk (ELCR) ranged from 0.0007 to 0.0012, with a mean of 0.0010. The total annual collective effective dose equivalent is 4839.49 person-Sv.  Conclusion: The AEDE in the study area is lower than the maximum permissible limit of 1 mSv y^-1 recommended by ICRP. The AEDE was higher in areas of high elevations than those of low elevations. It was estimated that about twenty-eight (28) of every one hundred thousand (100,000) persons are at risk of developing radiation-induced diseases per annum in the study area.