Adequate knowledge of the mechanical properties of fruits is required for the optimization of fruits harvesting robots. This study was carried out to evaluate some physical and mechanical properties of bell pepper fruits, which will be useful for the design and utilization of bell pepper fruits harvesting robots. Some mechanical properties (failure force, failure energy and compressibility) of matured bell pepper fruits were evaluated at three different dimension sizes and two fruit orientations, according to the American Society of Agricultural and Biological Engineers (ASABE) approved procedure. Results obtained from this study revealed that the fruit size and orientation had significant (p ≤ 0.05) effect on the mechanical properties of the bell pepper fruits. The failure force and failure energy of the fruit increased significantly (p ≤ 0.05) as the fruit locule number increases from 3 to 4. Relatively, the results revealed that the failure force and failure energy of the fruit increased significantly (p ≤ 0.05) as the fruit size increased from small to large size. As portrayed by this study results, the failure force and failure energy of the fruit when loaded in the natural position was higher than values obtained, when the fruit was compressed at the vertical position; irrespective of the fruit size. This revealed that the fruit at the natural position absorbed higher compressive force (pressure) and compressive energy, regardless of the fruit locule number. Results obtained from this study will present useful information for the design, programming and optimization of bell pepper harvesting and handling robots.