This study investigates the effects of substituting 70% of natural aggregate particles with Foamed Glass Synthetic Lightweight Aggregate (FG-SLA) in Hot Mix Asphalt (HMA), focusing on changes in the mixture’s cracking resistance, tensile strength, resistance to moisture-induced damage, and thermal conductivity. The results show that the inclusion of FG-SLA significantly reduces thermal conductivity, offering a potential benefit in improving frost protection. The substitution also led to improved cracking resistance in the mixture. Additionally, it enhances the mixture’s resistance to moisture-induced damage, as indicated by higher tensile strength ratios compared to the control mixture. However, a decrease in the dry tensile strength of the lightweight HMA can be recognized, highlighting a trade-off between moisture resistance and mechanical strength. These findings underscore the potential of FG-SLA in improving HMA performance, especially in applications where thermal properties and moisture resistance are critical. Although the results from this preliminary study are found to be promising, further research is needed to better understand the effects of varying levels of FG-SLA substitution, as well as its broader implications on thermal conductivity, mechanical properties, and economic feasibility.