<p>Hybrid nanofluids represent a novel class of nanofluids, created by dispersing various types of nanoparticles within a base fluid. This study presents an experimental analysis of how the temperature and nanoparticle concentration influence the thermal conductivity of graphene–multiwalled carbon tubes/distilled water, ethylene glycol, and distilled water/ethylene glycol (70:30) hybrid nanofluids. Graphene–multiwalled carbon tubes nanoparticles were characterized using field emission scanning electron microscopy and X-ray diffractometry techniques. The experiments were carried out to investigate the variation of thermal conductivity with temperature and volume fraction of nanoparticles. The temperature was varied from 30 to 60&#xa0;°C, while the volume fractions of nanoparticles at 0.001%, 0.01%, and 0.1% were observed. The improvement in the value of thermal conductivity with the increase in both the temperature and the volume fraction of nanoparticles was observed. It was observed that a higher volume fraction of nanoparticles and the elevated temperatures have a favorable effect on the thermal conductivity. Based on the experimental data, an empirical correlation was established for the prediction of thermal conductivity ratio of graphene–multiwalled carbon nanotubes/distilled water/ethylene glycol hybrid nanofluids using python code taking into consideration the hybrid nanofluids concentration, temperature, hybrid nanofluids, and base fluids thermal conductivity. The proposed correlation showed a good agreement between the experimental data and correlation within a margin of deviation of less than 10%.</p>