In this work, we have presented the numerical results for 2D, steady, laminar and incompressible flow in a square, two-sided, lid-driven cavity with a decentered heated triangular block (maintained at the isothermal thermal condition, TH) for non- Newtonian power-law fluids. The range of flow governing parameters considered for the numerical experimentations are Reynolds number (100 ≤ Re ≤ 1000), Richardson Number (Ri = 0.01, 1, 10) power law index; (0.2 ≤ n ≤ 1.8), blockage (10% and 30% of the height of cavity) and Prandtl number of Pr = 1. The upper and lower walls of the square cavity are kept moving in the opposite directions along –x axis (u−ux) and are thermally insulated. The left and right stationary walls are exposed to ambient condition (Tc). The governing flow equations are solved by using the finite volume approach and SIMPLE algorithm. Heat transfer characteristics and flow kinematics are revealed by systematic variation of streamlines and temperature contours. The effect of mixed convection parameter, i.e., Ri, found to have a negligible impact on fluid and thermal structure inside the cavity for fluids with n = 0.2.Heat transfer rate found to be lower for Ri = 0.01 for both blockages. © 2018 Elsevier Ltd