The perovskite structure BaSnO3 is regarded as a promising photoanode material, and an effective necking treatment strategy is necessary for the electrical connectivity of mesoporous BaSnO3 photoanode-based solar cells. The often-adopted necking strategy involves the treatment in TiCl4 solution with low pH, which can lead to the leaching of barium cations from BaSnO3 and impair the effect of the necking treatment. To address this issue, we report herein a novel noncorrosive necking strategy based on the common ion effect. The strategy involved treating the mesoporous BaSnO3 photoanode with a mixture solution of TiCl4 and BaCl2. Compared with the common TiCl4 necking treatment, the treatment with TiCl4 and BaCl2 mixture solution negligibly affected the formation of the TiO2 overlayer on the surface of BaSnO3 particles, but it maintained the crystallinity of the BaSnO3 particles. The TiCl4 and BaCl2 mixture solution treated BaSnO3 photoanodes were assembled into CdSe/CdS co-sensitized quantum dot-sensitized solar cells (QDSSCs), which showed ca. 37% increase in power conversion efficiency in comparison with the TiCl4 treated photoanode. The charge extraction, electrochemical impedance spectroscopy, and intensity-modulated voltage/photocurrent spectroscopy measurements showed that the QDSSCs fabricated from the TiCl4 and BaCl2 mixture solution treated BaSnO3 photoanode contained fewer trap states and exhibited less charge recombination and longer electron lifetime than those based on the common TiCl4 treated photoanodes, demonstrating the effectiveness of the noncorrosive necking treatment.