This time the demands of natural composite materials are growing rapidly to be used as a construction material. Agrostone and other natural fiber/filler-based composite materials are becoming the common construction materials in Ethiopia. One of constitute of an Agrostone is glass fiber (synthetic Fiber) has its own drawback high cost, non-degradability, so it need to find alternative natural based fiber and there was no trend of utilizing natural resource to improve waste disposal, mechanical properties and environmental sustainability. Therefore, the aim of this study is to develop an Agrostone filled with rice husk and bamboo fiber using a compression assisted hand lay-up mold technique and to investigate its tensile, compression, flexural and impact properties in order to determine the filler and fiber ratio that has the best mechanical properties. The raw materials used for specimen fabrication are magnesium oxide, activation solution, pumice, bagasse, rice husk, glass fiber and bamboo fiber. The ASTM standard experimental procedures were followed to determine the mechanical properties and the RSM model predictive method based on face centered central composite design (FC-CCD) packaged in Design Expert 13 (USA) was applied to optimize the mechanical properties. It consisted of two variables of three levels (−1, 0 and +1) for both rice husk and bamboo fiber (wt.%). In addition, wt.% bamboo fiber (A) and rice husk (B) were elucidated at a range of (0–2.2) and (0–7.03), respectively. Effect of inclusion of bamboo fiber and rice husk on Agrostone materials properties was analyzed. The results show that both bamboo fiber and rice husk significantly affect the mechanical properties of the an Agrostone and optimized result were found at 3.091wt.% RH and 1.358wt.% BB inclusion. Keywords: Agrostone; Optimum fiber-filler ratio; RSM; Mechanical properties; bamboo fiber; rice husk