It is known that aggregate shape properties influence the quality and performance of pavement materials. Yet, there is little information available on the effect of aggregate shape properties on the flexural strength of concrete, which is the main topic of the present study. Aggregate Image Measurement System (AIMS) was used to analyze three sizes of coarse aggregate and three sizes of fine aggregate obtained from three different sources. Portland cement concrete beams were prepared and tested for flexural strength using Universal Testing Machine (UTM) according to ASTM standards. A positive relationship with a high correlation was found between some aggregate shape properties (angularity and texture) and the flexural strength of the concrete. At the same time, an inverse relation with weak correlation was noticed between flexural strength and sphericity of coarse aggregates. Meanwhile, the 2-D form of fine aggregate showed a positive relationship with a weak correlation with flexural strength. Despite showing a similar trend of effects that shape properties have on flexural strength, the shape indices showed a better correlation with flexural strength than uncompacted void content, which is used as a measure of combined shape properties in the conventional indirect test methods. Results also suggested that the shape indices measured using the imaging technique can be a good alternative for the conventional methods.