Solar illuminated reactors have been used by several researchers for photocatalytic wastewater treatment. In this work, the light distribution in a solar illuminated slurry bubble column reactor was investigated using the Monte Carlo method. The model was validated using total refracted radiation (TRR) measurements at the unilluminated reactor wall. A fairly good agreement between the simulated and experimental TRR measurements was achieved. Bubbles were shown to affect the transmission of direct light much more than that of diffuse light. While the solar diffuse fraction and bubbles strongly affected the TRR at low catalyst loadings, they had a negligible effect on the overall light absorption. The catalyst significantly affected the light distribution with an optimal catalyst loading of 0.15 g/L being deduced from the simulation. An analysis of the local volumetric rate of energy absorption (LVREA) revealed fairly uniform light absorption along the axial direction. The radial LVREA profiles were nonuniform with the region of highest LVREA shifting from the unilluminated side of the reactor at low catalyst loadings to the illuminated side at high catalyst loadings. This study highlighted the rigor, accuracy, and utility of the Monte Carlo method for simulation of the solar light distribution.