This study investigates how climate policy uncertainty influences corporate investment behavior. Specifically, it focuses on listed firms in Korea over the period 2003 to 2022. To conduct the analysis, we construct a climate policy uncertainty (CPU) index tailored to the Korean context. Empirical findings reveal that rising climate policy uncertainty negatively impacts both corporate investments and R&D expenditures. This adverse effect is particularly evident in firms with high greenhouse gas emissions and those engaged in climate-unfriendly business activities. In contrast, the impact is significantly weaker in low-emission and climate-friendly firms. These results highlight the need for the Korean government to reduce climate policy uncertainty. Doing so is critical for encouraging corporate investment and supporting sustainable economic growth.