This research was conducted to study the effect of addition of eggshell powder on physical and mechanical properties of natural rubber/high density polyethylene/Mengkuang fiber/eggshell (NR:HDPE:(MK/KT)) powder hybrid composite. The preparation of composite utilized the method of melt blending, which was blended for 18 minutes at 135 ºC and rotor speed 50 r.p.m. The composites of NR:HDPE:(MK/KT) were prepared with 60:40:20 weight ratio. The mengkuang fiber/eggshell powder hybrid composites were prepared with 5, 10, 15, 20 weight % of fiber. Mechanical properties of the composites were investigated using tensile test and impact test. Results obtained indicates that hybrid composite of NR/HDPE with 15:5 weight ratio of MK/KT filler had the optimum performance. The tensile test shows a maximum tensile strength of 4.2 MPa for hybrid composite NR/HDPE with 15:5 weight ratio of composition of filler. Whereas, the impact test shows a maximum impact strength of 2.1 MPa for hybrid composite of NR/HDPE with composition of 10:10 MK/KT filler. The addition of eggshell powder has reduced the water uptake. Morphological study on the composites shows a good fiber distribution throughout the hybrid composites and the addition of the eggshell powder promoted better fiber-matrix interaction. In conclusion, the addition of eggshell improves the mechanical properties of the composites.