Mixed convection around rectangular structures has great scientific value with various industrial applications. In this study, heat transfer in the mixed convection regime around a tilted rectangular cuboid is investigated experimentally and numerically. The cuboid has adiabatic wall boundaries, except for its frontal wall which is set isothermal and facing downwards when tilted. The effect of an upcoming horizontal flow on mixed convection around the cuboid was investigated focusing on flow characteristics for Reynolds numbers in the range of 10(4) < Re < 1.8 x 10(5) with low turbulence intensities of TI < 5.5% and Richardson numbers of 5 x 10(-3) < Ri < 2, well within the mixed convection regime. A numerical simulation based on the three-dimensional SST k - omega turbulence model, validated against data from wind tunnel experiments, was used to accurately estimate the total heat transfer rate and the average Nusselt number as a function of cuboid inclination and wind direction at different Ri and TI. The results show that convective heat transfer is enhanced at a characteristic inclination of similar to 80 degrees by similar to 30% in comparison to the case where the freestream flow is perpendicular to the isothermal wall. Flow behaviour in the vicinity of the cuboid demonstrated that laminar separation and turbulent reattachment were responsible for this enhancement, which is a behaviour not observed for isothermal flat plates but reported for flows around cylinders and spheres. Crown Copyright (C) 2017 Published by Elsevier Ltd. All rights reserved.