This study investigates the influence of polypropylene (PP) fiber content on the mechanical properties of lightweight foamed concrete (LFC). Four LFC mixtures with a target dry density of 1000 kg/m³ were designed with different PP fiber volumes of 0%, 0.25%, 0.5%, and 0.8%. The fresh unit weight (UW), dry density, compressive and flexural strengths, water absorption, thermal conductivity, ultrasonic pulse velocity (UPV), and scanning electron microscopy (SEM) of the LFC were examined. The results indicate that the fresh UW, dry density, UPV, and thermal conductivity decreased when the PP content varied from 0% to 0.8%. At 28 days, the compressive and flexural strengths of the LFC increased approximately 11.85% and 41.8% when the PP fiber amount varied from 0% to 0.8%, respectively. The result implies that the PP fiber content had a higher influence on the flexural strength content than the compressive strength. Furthermore, the results of SEM could explain well the obtained mechanical properties. The findings of this study indicate that PP fiber could be used up to 0.8% by volume to reduce the self-weight of the LFC and enhance the mechanical strength as well as thermal isolation characteristics of the LFC.