In this study, polyaniline (PANI) nanocomposite-based nanofluids (NFs) in ethylene glycol were obtained with a two-step method by varying volume concentrations from 0.005% to 0.02%. Tungsten disulphide (WS2) nanoparticles were doped in PANI having different weight percentage (1%, 2% and 5%) via oxidative in situ polymerization employing ammonium persulphate oxidant in an acidic environment. The nanocomposites were comprehensively characterised using various techniques, such as Fourier transform infrared spectroscopy, thermogravimetric analysis, field emission scanning electron microscopy and high-resolution transmission electron microscopy. The formulated NFs were extensively investigated with zeta-sizer, particle size analyzer, thermal property analyzer and rheometer in a temperature range of 25 degrees C to 70 degrees C. The zeta potential results (up to 54.5 mV) were evident of extraordinary stability of NFs at all targeted temperatures along with polydispersity index <30% and mean particle/agglomerate size in the range of 335.8 to 489 nm. Additionally, a remarkable thermal conductivity improvement (similar to 20.7%) was achieved with intrinsic PANI-based NFs at an operating temperature of 50 degrees C. Subsequently, it varied substantially with WS(2)doping within PANI matrix and reached to 117.9%. Furthermore, the rheological measurements have revealed the viscoelastic nature of NFs along with a remarkable reduction in apparent viscosity (up to 8.4%). The temperature sweep viscosity indicated the transition of relative viscosity from high to low at a critical temperature of about 55 degrees C. The NF10 (WS2 + PANI 5, at 0.005 vol%) was found to be the best candidate with 63.8% thermal conductivity enhancement and 6.4% viscosity reduction as compared with the base fluid at an operating temperature of 50 degrees C. Thus, WS(2)doping within PANI has proved to be crucial in the proliferation of thermal conductivity and mitigation of viscosity.