An experimental investigation on the thermo-mechanical and moisture absorption properties of lightweight geopolymer concrete prepared with fly ash, NaOH, sodium silicate and Polypropylene Fibers (PF) is presented in this study. The effects of dry density, NaOH, PF, aggregates and hydrophobic agent on the compressive strength, thermal properties and moisture absorption were studied. Results indicate that thermo-mechanical properties of Fly ash-based Lightweight Geopolymer Concrete (FLGC) strongly depend on the dry density, NaOH, PF and aggregates contents. The increase in dry density and fine aggregate contents resulted in higher compressive strength and thermal conductivity. NaOH within mass ratio of 0-10% is able to enhance thermo-mechanical properties. The optimal compressive strength was achieved when the length and content of the PF was 12 mm and 0.5% respectively. Meanwhile, PF in the range of 0-1% can also increase thermal conductivity and enhance moisture absorption. The increase in coarse aggregate ranging from 0 to 15% led to reduced dry density and thermal conductivity and enhanced moisture absorption, but did not affect compressive strength. Interestingly, the decrease in fine aggregate with the same content had the opposite impact to the moisture absorption in comparison to the coarse aggregate. However, the moisture absorption can be considerably weakened by surface *Revised Manuscript Click here to view linked References waterproofing treatment which makes the enhanced thermal performance durable. Therefore, the FLGC reinforced by PF has excellent thermo-mechanical properties and can also be engineered to be an environmentally friendly and durable thermal insulation material with the assistance of waterproofing treatment.