<p>Accurately evaluating forest carbon sink efficiency and identifying the sources of regional disparities are crucial for enhancing the climate mitigation potential of forest ecosystems and advancing global carbon neutrality targets. This study employs panel data from 285 prefecture-level cities in China (2003–2021) to measure forest carbon sink efficiency using the Super-SBM model and to examine its spatiotemporal dynamics. The Spatial Durbin Model (SDM) is further employed to identify influencing factors and spatial spillover effects. Key findings reveal: (1) The national average forest carbon sink efficiency was 0.41, exhibiting a three-stage pattern of fluctuating growth, relative stabilization, and short-term decline. (2) Southwest China and South-Central China outperformed other regions, while North China and Northwest China remained below the national average. (3) The spatial pattern of forest carbon sink efficiency can be characterized as “high‑value embeddedness, low‑value dominance”. High‑efficiency regions were mainly distributed as point‑shaped clusters in the Northeast forest region and Southwest China, whereas low‑efficiency regions were concentrated in Northwest China, North China, and parts of East China. (4) Economic development and increased precipitation directly promote local forest carbon sink efficiency, whereas urbanization rate, the expansion of built-up areas, and scientific and technological input exert inhibitory effects. Industrial structure optimization, scientific and technological input, and transportation infrastructure demonstrate significant spatial spillover effects on forest carbon sink efficiency in neighboring regions. These findings provide a scientific basis for optimizing regional forest carbon sink management strategies and promoting cross-regional ecological coordination.</p>