Research on the development of lightweight concrete (LWC) utilizing wastes and natural resources as lightweight aggregates (LWA) is increasingly gaining attention worldwide due to sustainable and environmental concerns. A new alternative is using palm kernel oil polyol (PKO-p)-based polyurethane (PU) as filler. Rigid PU is a block copolymer comprised of a monomeric PKO-p and 2, 4-methylene diphenyl diisocyanate (crude MDI). The property of PKO-p, its ratio with crude MDI and reaction time were determined. The reaction time showed the average of 60 s for cream time and 95 s for rise time with maximum hardening time of 8 min. The reaction between PKO-p to MDI at 1:1 ratio resulted in a very short hardening time (within 2 min). The compressive strength of the rigid PU was at 7.0 MPa at a density of 206 kg/m3 . Further increase in the amount of PKO-p increased the density and compressive strength of the PU. PU aggregate in the concrete mixture was added at 1 to 5% (w/w) to obtain concrete with density of less than 1800 kg/m3 . The resulting concrete has excellent compressive strength (17.5 MPa) and thermal conductivity (0.24 W/m⋅K). The results showed that physical properties of PU played the most significant effect on the physical and mechanical properties of the lightweight concrete