One of big challenges in Egyptian pulp and paper sector is the exploring of new prospective for development and improvement the properties of paper made from Kraft bagasse pulp. The study utilized polyethylene terephathalate (PET) as reinforcement to the pulp made from Kraft bagasse to improve the paper properties. Increasing of the computability between PET fibers and Kraft pulp could be achieved by different partial hydrolysis processes for PET with sodium hydroxide, sulphuric acid, or ethanol amine. Optimum pretreatment conditions for different types of partial hydrolysis were identified to be used in formation of blended paper sheets with Kraft bagasse pulp. The study has investigated the effect of kind of pretreatment and concentration of PET on the mechanical, moisture uptake, and thermal aging for blended paper sheets made from PET fibers and Kraft pulp. The blended paper sheets using alkali pretreated PET manifested superior mechanical, thermal, and moisture resistance properties in comparison with paper sheets manufactured from blending with acidic, or amine pretreated PET.