The aim of the present study was to explore the influence of aiding buoyancy on mixed convection heat transfer in power-law fluids from an isothermally heated unconfined square cylinder. Extensive numerical results on drag coefficient and surface averaged values of the Nusselt number are reported over a wide range of parameters i.e. Richardson number, 0.1 ≤ Ri ≤ 5, power-law index, 0.4 ≤ n ≤ 1.8, Reynolds number, 0.1 ≤ Re ≤ 40, and Prandtl number, 1 ≤ Pr ≤ 100. Further, streamline profiles and isotherm contours are presented herein to provide an insight view of the detailed flow kinematics.