The combined utilization of fly ash and ground granulated blast-furnace slag as a partial cement substitution in the production of lightweight foamed concrete (LFC) incorporating different polypropylene (PP) fiber was investigated in this study. The LFC was prepared with a target dry density of 1200  50 kg/m3 and the influence of PP fiber contents (e.g., 0, 0.3, 0.6, and 1.0% by volume) on the characteristics of LFC was examined in terms of fresh unit weight, dry density, water absorption, thermal conductivity, compressive strength, flexural strength, ultrasonic pulse velocity (UPV), and microstructural analysis using scanning electron microscopy (SEM) technique. Results show that the inclusion of PP fiber affected all of the studied characteristics of LFC. Increasing PP fiber percentages resulted in reducing dry density, thermal conductivity, and UPV. Whereas, both the mechanical strength and water absorption were found to be increased with PP fiber content. The result of the SEM analysis also supported these findings. At 28 days, all of the LFC obtained the target dry density of 1200 +/- 50 kg/m3, satisfying the requirements of TCVN 9029:2017. The water absorption, thermal conductivity, UPV, compressive strength, and flexural strength values of the LFC specimens were recorded at the respective ranges of below 10%, 0.394–0.461 W/mK, 2955–3019 m/s, 15.98–17.33 MPa, and 2.31–4.07 MPa. Furthermore, the results suggested that 1.0% PP fiber was the most suitable level for the production of LFC.