Abstract: The expansion of farmland transfer has profoundly reshaped China’s agricultural landscape, giving rise to a growing group of external large-scale farmers who lease land across administrative and social boundaries. Ensuring that these external operators adopt green production technologies is crucial for achieving sustainable agricultural transformation. However, despite their increasing prominence, the mechanisms through which land tenure arrangements and social contexts influence their green technology adoption remain insufficiently understood. This study aims to fill this gap by examining how the stability of farmland transfer operational rights affects external large-scale farmers’ green technology adoption behaviors, with a particular focus on the mediating role of risk perception and the moderating role of village embeddedness. Grounded in property rights theory and embeddedness theory, this study conceptualizes tenure stability as a multidimensional construct encompassing legal, factual, and perceived security of operational rights. The analysis draws on micro-level survey data from 378 external large-scale farmers in Fujian Province, employing ordinary least squares (OLS) regression and mediation models to test the proposed hypotheses. To ensure robustness, the study further applies 5% percentile Winsorization, variable substitution, and instrumental variable (IV) techniques. Empirical results demonstrate three major findings. (1) Tenure stability significantly promotes green technology adoption across all three dimensions. Legal security (e.g., formal contracts and enforceable rights) provides institutional guarantees for long-term investment; factual stability (e.g., stable use and minimal disputes) ensures operational continuity; and perceived stability (e.g., subjective confidence in land retention) shapes behavioral expectations. Together, they strengthen external farmers’ willingness to commit to sustainable production. (2) Risk perception mediates the relationship between tenure stability and technology adoption. When farmers perceive their operational rights as secure, they are less likely to view green production technologies as risky or uncertain, thus reducing psychological barriers to adoption. (3) Village embeddedness exerts significant moderating effects. Stronger embeddedness—reflected in trust-based relationships, reputation networks, and reciprocal cooperation within rural communities—attenuates the negative influence of perceived risk and reinforces the positive impact of tenure stability on adoption. In contrast, weakly embedded farmers face higher social transaction costs, limited access to information, and lower credibility in cooperative arrangements. These findings advance the literature in several ways. First, the study establishes an integrated analytical framework linking institutional security, risk cognition, and social embeddedness, thereby bridging the divide between formal property rights and informal rural governance. Second, it provides rare micro-level empirical evidence on the behavioral mechanisms of external large-scale farmers, a group often marginalized in land and sustainability research. Third, it highlights the dual governance logic of “institutional incentives and relational embeddedness”, offering new insights into how formal and informal systems jointly shape ecological behaviors in transitional rural economies. Policy implications are twofold. On the institutional side, enhancing the stability and enforceability of farmland transfer contracts can strengthen investment incentives and reduce perceived risks for external operators. On the social side, governments and local organizations should encourage inclusive community integration, fostering shared values, mutual trust, and benefit-sharing mechanisms between migrant farmers and local residents. Together, these efforts can promote a virtuous cycle of secure tenure, reduced risk, and sustainable agricultural innovation.