Background and aims <p>Seedling recruitment is crucial for maintaining species diversity and coexistence in long-term vegetation dynamics. However, the knowledge of interactions between environmental factors and seed traits affecting this process under climate change remains limited.</p> Methods <p>We investigated seed traits, including seed mass, shape, and germination characteristics across 50 alpine plant species in the laboratory. A field experiment using open-top chambers (OTCs) was conducted to assess seedling recruitment (emergence and establishment success) under ambient and warming conditions. Phylogenetic signals were assessed using Pagel’s λ and phylogenetic generalized least squares (PGLS). Phylogenetic multiple regression was employed to explore the relationships between seed traits and recruitment success, and shifts under warming.</p> Results <p>Our study provides the first comprehensive evidence that larger, elongated/flattened, non-dormant seeds with higher germination rates consistently achieved higher recruitment success compared to smaller, compact and dormant seeds in both warming and ambient conditions. Warmer and drier conditions altered the importance of seed traits in contributing to recruitment success: in ambient conditions, seed shape index (<i>R</i>^<i>2</i> = 0.070) was the primary predictor, whereas under warming, seed mass (<i>R</i>^<i>2</i> = 0.168) and germination time (<i>R</i>^<i>2</i> = 0.066) became stronger predictors, with seed mass contributing the largest impact.</p> Conclusions <p>Key seed traits—seed mass, shape, and germination time—critically predict seedling recruitment success under climate warming on the Tibetan Plateau. Warming increasingly favors large-seeded species, highlighting the importance of seed mass in recruitment success. Accurate predictions of seedling dynamics under climate change require integrating multiple seed traits and their interactions with environmental conditions.</p>