Abstract: Full-chain digitalization in agriculture involves integrating digital technologies into every stage of the agricultural industrial chain and serves as a key driver of agricultural modernization and the upgrading of the agricultural socialized service system. Based on panel data from 30 Chinese provinces for the period 2011 to 2023, this study measures the levels of full-chain agricultural digitalization and agricultural socialized service provision. This paper employs the fixed-effect model, the mediation-effect model, and the threshold-effect model to systematically examine the mechanism through which full-chain agricultural digitalization improves the quality and efficiency of agricultural socialized services. The results indicate that: 1) full-chain agricultural digitalization significantly improves the level of agricultural socialized service provision, and this finding remains robust after a series of robustness checks and endogeneity treatments; 2) it promotes the development of agricultural socialized services primarily by facilitating rural human capital, fostering agricultural technological innovation, and encouraging large-scale agricultural operations; 3) its positive effect is more pronounced in the eastern and central regions and in major grain-producing and -consuming areas; 4) the digitalization of agricultural circulation and public services has a stronger positive effect, whereas infrastructure digitalization plays a relatively limited enabling role; and 5) the impact of full-chain of agricultural digitalization on agricultural socialized service provision exhibits significant nonlinear threshold effects. Based on these findings, this paper suggests that concerted efforts should be made to build a digital agricultural ecosystem, cultivate service providers, strengthen regional coordination, and develop innovative mechanisms to promote the high-quality development of agricultural socialized services.