In the present study, different series of High Density Polyethylene (HDPE)/carbon nano-composites were prepared using melt blending in a co-rotating intermeshing twin screw extruder. The morphological, thermal, rheological, viscoelastic, mechanical, and fracture toughness properties of the nano-composites were analyzed. The microscopic examination of the cryogenically fractured surface found a good distribution of carbon nano-particles in the HDPE matrix. The melting temperature was not significantly affected by the addition of nano-carbon. Whereas, the crystallization percentage was slightly affected by adding carbon nano-particles into the matrix. The complex viscosity increased as the percentage of carbon increased. The Dynamic Mechanical Analysis (DMA) showed that the storage modulus increased with increasing the carbon nano-particles ratio and with increasing the testing frequency. The tensile test results showed that with increasing the carbon nano-particles contents, the Young's modulus, yield strength of HDPE nano-composite increased while the strain at fracture decreased. Similarly, the fracture toughness and the strain energy release rate decreased proportional to the carbon content.