<p>Green food certification (GFC) represents a critical step toward achieving sustainable agricultural practices. However, its adoption among kiwifruit farmers in China remains limited, primarily due to financial constraints and varying levels of social capital. This study investigates kiwifruit farmers’ willingness to adopt (WTAd) and willingness to pay (WTP) for GFC, focusing on the role of social capital in shaping their decisions. Data were collected from 404 kiwifruit farmers in major kiwifruit-producing Provinces using a structured household survey. A non-parametric contingent valuation method estimated the expected WTP, while a double-hurdle model analyzed the impact of social capital on WTAd and WTP. Results showed that 52% of kiwifruit farmers were willing to adopt GFC, while only 34% were willing to pay for it, with the average WTP being CNY 912.24 per household per year. Key social capital factors, including network strength and institutional trust, were significantly associated with farmers’ WTAd and WTP. Additionally, training and perceived benefits positively impacted both WTAd and WTP, while socio-demographic factors such as age, education, and household labor availability exhibited nuanced effects. These findings highlight the critical role of social capital in promoting GFC adoption. Policymakers are encouraged to provide financial incentives, strengthen social networks, and enhance farmer training programs to bridge the economic and informational gaps that hinder the widespread adoption of sustainable practices.</p>