Bamboo fiber-reinforced "green" composites were fabricated by using a conventional hot pressing method. Their insulating properties were evaluated by the value of thermal conductivity, which was measured using a hot wire method. It was demonstrated that thermal conductivity of bamboo fiber reinforced "green" composites is smaller than that of conventional GFRP (glass fiber reinforced plastics) and CFRP (carbon fiber reinforced plastics). The thermal conductivity of "green" composites was significantly influenced by their density as observed in woods.