High density polyethylene (HDPE) is a thermoplastic material that is characterized as a semi-crystalline polymer. Density, molecular weight and molecular weight distribution (MWD) dominate the resin properties that influence the manufacture of the polyethylene products and the subsequent performance of them. Resins with a broad range of distribution have good impact resistance and good processability. A polymer with a narrow MWD contains molecules that are nearly the same in molecular weight. Polymers can also have a bimodal shaped distribution curve. Resins having a bimodal MWD contain both very short and very long polyethylene molecules, giving the resin excellent physical properties while maintaining good processability. In this research, two blow molding grade of HDPE (BL3) with the same specifications (melt flow rate (MFI) range and density) that those produced by different manufactures were compared and studied. The MWD of the BL3 samples were studied with Gel permeation chromatography (GPC) and Capillary Rheometer (CR). Differential scanning calorimetry (DSC) was used to study the thermal properties and the Notched impact test used to study Impact Strength. The GPC results have shown that both samples, had similar bimodal shaped distribution curves, but curve of sample 2, located partially in the higher range of MWD (placed in the higher quantities on the horizontal axis (molecular weight)) than the sample 1. The CR results also showed that both samples, had similar distribution, but the sample 1 shows better processability in the blow molding shear rate range than the other sample. This was observed because the sample 1 included the lower molecular weights than the sample 2. The DSC results have shown that sample 2 had higher crystallinity and Tm than the other sample. Notched impact test results also showed that the sample 2 had higher impact resistance. Results showed that sample with the higher range MWD, had better thermal and physical-mechanical properties.