Cement kiln dust (CKD) is produced in the kiln as a byproduct during the production of cement clinker. CKD is undesirable material for a clean environment. The main purpose of this study was to evaluate the feasibility of using CKD, a byproduct of cement manufacturing, to improve engineering properties of hot mix asphalt (HMA). The study evaluated the effect of replacing the limestone filler in the asphalt limestone HMA mixes and asphalt basalt HMA mixes by CKD. A comparison study was made to compare the effect of replacing the filler by CKD on the mechanical properties of the asphalt mortar (asphalt cement with mineral filler) and HMA mixes. The test results showed that CKD increased the softening point and viscosity of the asphalt cement; however, no changes were required in the mixing procedure nor time of mixing for the HMA mixes. The inclusion of the CKD resulted in an increase of the optimum binder content of the HMA mixes with improving the asphalt resistance for stripping and an increased fatigue life and indirect tensile strength. In addition, the diametral resilient modulus was improved by 130% and 144% for the basalt and limestone mixes, respectively. Moreover, the research proved that the inclusion of CKD in asphalt mixes has no adverse environmental effects on neither the underneath soils nor the underground water.