The mixture of the traditional cement mortar is mainly made from three components; ordinary Portland cement (OPC), sand and water. However, the OPC has many proven adverse effects on the environment and economy, such as harmful emissions and depletion of natural sources. Therefore, some studies try to minimise the use of OPC in cement mortar by providing and testing some alternatives, such as Cement Kiln Dust (CKD). The available studies confirm the applicability of CKD as a promising alternative to OPC in cement mortar. This study will explore the effects of different percentages of CKD (10-30% of OPC amount) on the Ultrasonic Pulse Velocity (UPV) in the cement mortar's properties. This study showed that adding CKD as a partial replacement for OPC decreases the UPV compared to the reference sample.