Conventional stone mastic asphalt (SMA) is being increasingly used in highways and expressways because it provides high rutting resistance, good skid resistance, and noise reduction for heavily trafficked roads. However, the conventional SMA mixture requires high mixing and compacting temperatures to create a suitable coating between the polymer-modified asphalt and large size of aggregate. Warm-mix asphalt (WMA) technology is being extended to provide significant economic benefits when applied to heat sensitive mixture, such as polymer-modified mixture, to reduce mixing and compacting temperatures. In this study, the performance characteristics of SMA–WMA mixture using new polyethylene wax-based WMA additive were evaluated against the conventional SMA mixture without additive, in terms of the moisture susceptibility, viscoelastic properties, rutting resistance at high temperature, fatigue resistance, and crack resistance at low temperature. The mix design was carried out in the laboratory for the conventional SMA mixture, and a similar composition was adopted for the SMA–WMA mixture (with the incorporation of 1.5 % WMA additive in the asphalt binder weight), in order to evaluate the influence of the performance characteristics of the resulting SMA mixture. Drain-Down and Cantabro test results of SMA–WMA mixture meet the requirement of the relevant criteria. Compared to the conventional SMA, the mixtures containing WMA additive show superior performance in moisture susceptibility, rutting resistance at high temperature, fatigue resistance at intermediate temperature, and crack resistance at low temperature. Therefore, this implies that the WMA additive is effective in reducing the production temperature, without compromising the performance of the SMA–WMA mixture.