As a key market-based instrument for low-carbon transition, China’s national carbon emission trading market facilitates emission abatement and reshapes labor allocation in regulated firms. Based on the task-based framework, a task embedding hypothesis is proposed. Restricted by organizational adjustment costs, firms tend to integrate green compliance tasks into existing roles instead of massively establishing specialized green positions. Using 13 million job postings and matched financial data of Chinese A-share listed firms from 2016 to 2024, this study regards the launch of the national carbon market as a quasi-natural experiment and adopts a difference-in-differences (DID) approach. The results indicate that the carbon market raises the green job share of regulated enterprises by 4.7 percentage points. Such growth is not driven by newly built environmental departments. Management compliance posts decrease markedly, technical posts remain stable, while task-embedding positions combining traditional and green tasks dominate the growth effect. Heterogeneously, private enterprises and eastern China dominate the transformation, while state-owned enterprises lag behind and central and western regions witness a green job share decline. This study enriches task-based theory application in environmental regulation and provides empirical implications for sustainable green talent development and just transition policy design.