The effect of different nanofluid thermal conductivity models on the mixed convection flow and heat transfer in a lid-driven square enclosure heated from the left vertical wall and cooled from the top wall was investigated numerically in this study for various values of the governing parameters. The Al2O3 was assumed as nanoparticle and ethylene glycol-water mixture as the base fluid. Three different nanoparticle volume fractions were taken into consideration: 0%, 4% and 8%. Four different volume ratios of EG to water were considered: 0:100%, 40:60%, 60:40% and 100:0%. The Grashof number was assumed constant at a value of 104 and the Reynolds number was varied in a range so that the Richardson number takes values in the range of 0.1 to 10. The results show that the average Nusselt number has a linear dependency on the nanoparticle volume fraction for all the thermal conductivity models considered in this study. The results also show that the thermal conductivity models produce considerably different average Nusselt numbers. The results also indicate that the average Nusselt number from the highest to the lowest is for: Pak and Cho model, Yu and Choi model, Ghanbarpour et al. model, Maxwell model, and Timofeeave et al. model. The results finally show that Pak and Cho model yields considerably higher average Nusselt numbers than the other models. (C) 2016 Published by Elsevier B.V.