The impact of partial shading on the light distribution and associated efficiency reduction on side-mounted solar cell strips in square luminescent solar concentrators (LSCs) is investigated. Combining experimental testing and ray-trace model simulations the effects of partial shading on the LSC electrical performance were assessed at different locations of the LSC waveguide and proximity relative to the solar cell strip. It was found that electrical performance was affected in a non-linear manner: shading closer to the solar cell strip resulted in a significant reduction in performance with variations depending on the location, while shading further away led to a less severe decrease in conversion efficiency. For an LSC with four side-mounted solar cell strips, it is found that shading at the center of the LSC waveguide results in higher efficiency compared to shading at the edges or corners. This can be explained as central shading affects all solar cells strips uniformly, thus reducing the mismatch in photogenerated currents in the solar cell strips. Conversely, corner shading resulted in the lowest efficiency due to the direct disruption of photogenerated currents in multiple solar cell strips simultaneously. A photon distribution analysis from ray-tracing confirmed that shading near the edges of the LSC leads to local reductions in photon numbers, while central shading disrupts light distribution more uniformly across an LSC with four solar cell strips.