Due to the ever-increasing complexity of engineering products, there is a growing need to utilize composite materials, such as polymers and metals, in order to develop cost effective and/or optimized designs. Therefore, adhesive bonding of thermoplastics to metals has attracted the attention of the scientific community as well as many industries such as automotive, construction, oil and gas, etc. This research is focused on improving the adhesive bonding strength between high density polyethylene (HDPE) and aluminum in demanding service conditions such as elevated temperatures (up to 82°C), prolonged exposure to harsh chemicals, and high-pressure gasses, which are typically encountered in pipelines used for oil and gas transportation. A maleic anhydride-grafted linear low-density polyethylene (MA-g-LLDPE) was used as the adhesive layer between HDPE and aluminum. The effects of inclusion of well-dispersed graphene nanoplatelets on the adhesive properties of MA-g-LLDPE were investigated. Morphological observations were carried out to demonstrate high levels of dispersion of graphene within the adhesive. It was observed that the inclusion of an optimal amount of graphene in the MA-g-LLDPE adhesive layer led to significant improvement of the bond strength (pull-off strength) between the adhesive and aluminum under all testing conditions. For instance, the high temperature (82°C) pull-off strength between the MA-g-LLDPE and aluminum was improved by over 40% after the inclusion of 1 wt.% of graphene nanoplatelets. The viscoelastic and mechanical properties of the MA-g-LLDPE/graphene nanocomposites, with different graphene contents, were tested at different temperatures to develop an understanding of the mechanisms that contribute to its adhesive performance.