Mesoporous perovskite solar cells (MPSCs) suffer from various types of charge carrier losses, where shunt losses usually dominate. Herein, we perform a systematic study to investigate the impact of such losses on the photovoltaic performance of methylammonium lead iodide (MAPbI(3))-based MPSCs. The shunt losses in the MPSCs are attributed to the leakage current and the non-geminated recombination losses. We also demonstrate that these losses can be reduced by the incorporation of appropriate thickness of compact titanium oxide (c-TiO2) interlayer between FTO and mesoporous TiO2 (m-TiO2). As a result, MPSCs exhibit higher open-circuit voltage (V-OC) of 1.05 V, short-circuit current density (J(SC)) of 23.27 mA cm(-2), and the power conversion efficiency (PCE) of 17.69% under one-sun illumination conditions. The improved device performance was attributed to (i) the efficient blocking of holes, (ii) the decrease of leakage current, and (iii) the suppression of the non-geminated recombination losses in the cells. The effect of the c-TiO2 layer thickness on the series resistance (R-S), shunt resistance (R-Sh), and the non-geminated recombination were also discussed in detail.