Due to the increasing risk of concrete structure collapse in Nigeria, it becomes important to know how the gradation of aggregates used in concrete mix affects the compressive strength of concrete. This study was carried out to determine the effect of aggregate gradation on the compressive strength of concrete. Concrete was prepared using a constant mix ratio of 1:2:4 and a constant water/cement ratio of 0.5 and then varying the gradation of the aggregates to obtain a well-graded aggregate distribution where aggregate sizes of 12mm, 19mm and 25mm were used, poorly-graded aggregates distribution where aggregate sizes 5mm, 10mm and 19mm were used and 19mm aggregate size being dominant and finally uniformly-graded aggregate distribution where only 19mm aggregate size was used. For the three aggregate gradation which are well-graded, poorly-graded and uniformly-graded, twelve concrete cubes were cast and tested for compressive strength on 7, 21 and 28 days of age.