A water-soluble fraction of bamboo ranging from 9.2 to 23.5 wt% was obtained by hot-compressed water (HCW) treatment as the temperature increased from 140 to 180 °C. Both untreated and HCW-treated bamboo fibers (BF) were then compounded with polypropylene (PP), either with or without the addition of 5 phr maleic anhydride-grafted PP (MAPP), to net a total BF content of 50, 30, or 10%. It was found that both the HCW treatment and the MAPP addition effectively improved the tensile properties of the composite. Furthermore, the re-compounding of 70/30 and 90/10 composites from a 50/50 master batch proved to be more effective in improving the tensile properties than the direct compounding of PP and non-or HCW-treated BF to the same composition.