Due to its superior mechanical properties compared to many other materials, reduced graphene oxide (rGO) shows great promise as a filler in polymer matrix nanocomposites. Through experimental investigation, this study explores the influence of rGO on the thermal and mechanical properties of high temperature resistance polyethylene (PE-RT). PE-RT/rGO nanocomposites were prepared by the melting method at 180 °C and screw speed of 100 rpm, with a residence time of 6 min. The results showed that there was an increase in the thermal stability of the nanocomposite at 8 °C. The DSC analysis did not reveal any substantial effect on the melting and crystallization temperatures or the degree of crystallinity of PE-RT; however, the XRD analysis revealed a higher crystallinity index for the sample with lower rGO content. SEM images showed that the GO nanoparticles have a good interface with PE-RT without agglomeration. The water contact angle values increased from 97.5° in the pure matrix to 102° in the nanocomposite, indicating that the nanoparticles increased the hydrophobicity of the material. Permeability assessments for CO2 showed an increase in time-lag of 6.01 hours. The aging test showed that rGO improves the performance of the PE-RT matrix against swelling. Hardness increased from 50 to 57 Shore D with 2.0 wt% rGO. Finally, the incorporation of 1.0 wt% rGO showed an increase in Young's modulus from 329±37 MPa to 419±40 MPa. The results suggest a potential gain in the use of rGO as reinforcement for PE-RT, which is beneficial for riser applications.