Experimental and numerical studies have been carried out to determine the impact of tilt angle on buoyancy-driven mixed convection coupled to surface radiation heat transfer inside a vented cavity. The present investigation might be rationalized in the thermal design of the electronic equipment housing, solar collector receiver, regenerative heating/cooling system, etc. Keeping the constant ventilation size and its location, the tilt angle measured from horizontal is varied from 0 deg to 90 deg with the increment of 15 deg. The experimental investigation comprising planner symmetry is complemented with the two-dimensional numerical study incorporating the range of Rayleigh number from 7.21 × 108 to 1.75 × 109, Reynolds number from 665 to 9931, Richardson number from 20.1 to 2283.4, and the surface emissivity from 0.05 to 0.85. The results signify that the convective Nusselt number enhances significantly at the optimum tilt angle of 90 deg, whereas the moderate increment in radiative Nusselt number is found at the optimum tilt angle of 0 deg. Based on the obtained experimental data, the empirical correlations of the average convective Nusselt number and dimensionless temperature are developed in terms of Reynolds number, Richardson number, and tilt angle.