Tests were performed to evaluated the feasibility of using Impact-Echo Method (IEM) in detecting defect and determining its depth during the early age concrete. Five Reinforced Concrete (RC) slabs grade 30 and 40 specimens respectively at day 3, 7, 14 and 28 with a fabricated void at a known location were used. The results obtained were analyzed to determine the accuracy of the method hence the effectiveness of it. Impact Echo method detect defects in specimens during early the age. Porosity has significant effect on the accuracy since lower porosity yield accurate determination of the depth of defect. Tests were also performed to examine the relationship between the porosity and strength of concrete at each stage with the accuracy of void depth detected. The test results indicate that the method can be used to assess the in-situ properties of concrete or for quality control on site. Impact Echo Test method showed better accuracy in detecting defect with stronger concrete with the accuracy ranging form 60.75-99.05% form day 3-28 (full strength) respectively.