The rapid urbanization in China has led to a substantial expansion of construction activities, causing notable energy consumption and a consequent rise in CO2 emissions. This study proposes an approach to assess CO2 emission efficiency in China’s construction industry by integrating data envelopment analysis cross-efficiency and the Nash bargaining game, considering CO2 as a fixed-sum undesirable output. The study identifies Jiangsu and Beijing as top performers, establishing benchmarks for other provinces. In contrast, Inner Mongolia displays the lowest efficiency. Generally, most provinces exhibit room to improve environmental efficiency in the construction sector. The study provides policy implications and tailored suggestions for specific provinces.