<p>As monopolists of land supply and responsible for carbon reduction, local governments can utilize low-carbon land supply strategies to affect carbon emissions. However, the effectiveness of these strategies remains unclear. This paper introduces the terms land-based fiscal revenue (LF) and land-based investment (LI) for land supply strategies and analyzes the spatial impacts of land supply strategies on CO₂ emissions using Chinese city-level data from 2003 to 2017. Results show that land supply strategies directly increase CO₂ emissions locally and in adjacent regions. Land-based fiscal revenue has a more robust negative externality in neighboring cities than land-based investment, which signifies a more competitive dynamic and intensified spatial interactions among local governments in land-based fiscal revenue. The land-based investment has revealed considerable heterogeneity across different regions. Western regions and underdeveloped cities are more likely to cause low-quality competition in land-based investment. Further analysis of the mechanisms reveals that environmental regulation is effective in curbing CO₂ emissions from land-based investment, and urbanization primarily affects the CO₂ emissions associated with land-based fiscal revenue. Meanwhile, financial development exerts differential impacts on land supply strategies and their associated carbon emissions. These findings confirm the specific role of land supply strategies in determining carbon emissions in Chinese cities and reveal the interactive effects of multiple mixed factors involved. Our study provides empirical support for city managers to balance land use and environmental management.</p>