The use of plastics, especially High-Density Polyethylene (HDPE) film has increased rapidly in recent years due to its low cost, lightweight and excellent mechanical properties which is depended on the extrusion condition in the owner’s film fabrication machine. The blown film process is the common process used to make a thermoplastic film in large volumes. However, many research performed long ago in the mechanical properties of polyethylene only concerned on the effect of conventional processing parameters such as temperature and pressure in blown film machines and neglected the significant effect of critical extrusion conditions. We did the study to know the effect of critical extrusion conditions such as output rate, blow-up ratio (BUR) and neck-point height (NPH) which was intended to get the optimum film fabrication conditions in a blown film extrusion machine. Each parameter was performed in five different conditions by increasing one parameter and controlling the other. The resin first melted, conveyed, and delivered before finally blown to form the film. The mechanical properties observed were impact resistance, tensile strength, elongation, tear strength, and young modulus. The result indicates that increasing the output rate, BUR and NPH imparted in the film’s orientation balance, bubble shape, relaxation, and crystallization effects will lead to the increase of impact resistance, decrease of tear strength, and balance of film direction properties. The excessive and low amount of output rate, BUR and NPH are not desirable as it decreases the mechanical properties from HDPE film whether in mechanical direction or transverse direction. Hence, the optimum operating condition depends on which mechanical properties that needed to be achieved by film fabricators.