Hybrid composite boards were manufactured from oil palm trunk (opt), frond (opf), empty fruit bunces (efb) and polyethylene. The objective of this study was to measure the thermal conductivity of hybrid composite boards. The thermal conductivity of the boards was measured using Quick Thermal Conductivity Meter (QTM-D3). In this study, hybrid boards with different types of oil palm fibres and plastic content (5%, 12% and 20%) were used as the samples for experiment. Statistical analysis showed that the fibre types did not affect thermal conductivity values significantly. However, fibre types did influence the density of the boards. The correlation between density and thermal conductivity showed that density affected the values of thermal conductivity but it was not significant. The results showed that the values of thermal conductivity for this type of hybrid board were very low. Therefore, the hybrid composite boards are suitable for use an insulating boards.