Utilizing sunlight to convert CO<sub>2</sub> into chemical fuels could simultaneously address the greenhouse effect and fossil fuel crisis. ZnSe nanocrystals are promising candidates for photocatalysis because of their low toxicity and excellent photoelectric properties. However, pristine ZnSe generally has low catalytic activities due to serious charge recombination and the lack of efficient catalytic sites for CO<sub>2</sub> reduction. Herein, a ZnSe nanorods-CsSnCl<sub>3</sub> perovskite (ZnSe-CsSnCl<sub>3</sub>) type II heterojunction composite is designed and prepared for photocatalytic CO<sub>2</sub> reduction. The ZnSe-CsSnCl<sub>3</sub> type II heterojunction composite exhibits enhanced photocatalytic activity for CO<sub>2</sub> reduction with respect to pristine ZnSe nanorods. The experimental characterizations and theoretical calculations reveal that the efficient charge separation and lowered free energy of CO<sub>2</sub> reduction facilitate the CO<sub>2</sub> conversion on the ZnSe-CsSnCl<sub>3</sub> heterojunction composite. This work presents a type II heterojunction composite photocatalyst based on ecofriendly metal chalcogenides and metal halide perovskites. Our study has also promoted the understanding of the CO<sub>2</sub> reduction mechanisms on perovskite nanocrystals, which could be valuable for the development of metal halide perovskite photocatalysts.