The mixed convection from a heated sphere for an arbitrary flow incident angle (theta) at low to moderate Reynolds numbers (1 <= Re <= 100) and Richardson numbers (0 <= Ri <= 5) is studied by an immersed boundary method, thereby investigating the influence of different flow incident angles (0 <= theta <= 180 degrees) on the buoyancy flow and heat transfer. The numerical method is validated by comparing the results with the simulation results of pure forced convection as well as those of mixed convection with assisting flow (0 degrees flow incident angle) published in the literature. Extensive simulations for a wide range of different incident flow angles have been performed. New correlations are obtained for the overall Nusselt number (Nu) in terms of theta, Ri, and Re, showing a quadratic decrease in Nu with respect to theta only for 0 degrees <= theta <= 0 90 degrees (aiding and cross flow) and a half bell-shaped decrease in Nu for 90 degrees < theta <= 180 degrees (opposed flow). The combined treatment of mixed convection for the completely upward flow, cross flow, and completely downward flow (i.e. at incident angle 0 degrees, 90 degrees and 180 degrees, respectively) was achieved showing almost linear relationships between the heat transfer rates and Ri for Ri >= 1. Published by Elsevier Ltd.