Concentrated solid‒solution alloys (CSAs) demonstrate excellent mechanical properties and promising irradiation resistance depending on their compositions. Existing experimental and simulation results indicate that their heterogeneous structures induced by the random arrangement of different elements are one of the most important reasons responsible for their improved properties. Nevertheless, the nature of this heterogeneity remains unclear. Here we scrutinize the role of heterogeneity played in damage evolution in different aspects through atomistic simulations. Different effects induced by atomic-level heterogeneity are considered, including lattice misfit, thermodynamical mixing, point defect energetics, point defect diffusion, and dislocation properties. Our results reveals that the defect evolution in CSAs only has weak relations with most of these parameters, suggesting the complexity of defect dynamics in these complexed alloys. However, our results indicate that defect properties may be the most important factors in influencing the irradiation performance of CSAs.