Seedling recruitment plays a key role in determining species composition and diversity. Exploring patterns of seedling dynamics can therefore provide crucial insights into the mechanisms that affect seedling recruitment. The broad-leaved Korean pine (Pinus koraiensis) mixed forest is a temperate forest typical of northeast China. In 2007, we established a 1 hm² plot in a broad-leaved Korean pine mixed forest on Changbai Mountain, northeast China. We identified, tagged, and mapped each tree with diameter at breast height ≥ 1 cm. At the same time, we set up 100 seedling quadrats of 1m×1m which were censused every July. In total, we collected data on 1288 adult trees and 965 seedlings in the 1 hm² plot between 2012 and 2013, and examined the importance of biotic and abiotic factors on seedling survival using a generalized mixed linear model. Biotic factors included presence of conspecific seedling neighbors and heterospecific seedling neighbors, presence of conspecific adult neighbors and heterospecific adult neighbors, and herb density and herb cover. Abiotic factors included soil organic matter, available soil phosphorus, available soil potassium, available soil nitrogen, total soil nitrogen, and canopy openness. Conspecific neighbors had a significant negative effect on seedling survival at the community level, indicating significant negative density-dependence effects. The effects of biotic and abiotic factors on seedlings differed with seedling age. Conspecific adult neighbors and canopy openness had significant positive effects on survival of, 1-year seedlings while heterospecific adult neighbors had a significant negative effect. In contrast, for 2- to 3-year-old seedlings, conspecific seedling neighbors and conspecific adult neighbors showed a significant negative effect on seedling survival, but abiotic factors had no significant effect. Moreover, for ≥ 4-year-old seedlings, soil PC axis 1 (associated with low organic matter available K, available N, and total N) showed a significant negative effect on survival. Factors that drove seedling survival varied with species dispersal-mode. For wind-dispersed species, conspecific seedling neighbors had a significant positive effect on seedling survival. For gravity-dispersed species, soil PC axis 3 (associated with high available N and total N, heterospecific adult neighbors, and herb density) had a significant negative effect on survival, whereas canopy openness showed a significant positive effect. The effects of biotic neighbors and habitat differed among species. For instance, soil PC axis 3, heterospecific adult neighbors, and herb density had significant negative effects on seedling survival of Tilia amurensis, while soil PC axis 2 (associated with high organic matter and total N) showed a significant positive effect. Finally, herbs might influence seedling survival. Both herb density and herb cover impacted seedling survival by modifying local habitat. However, there was no significant effect of herbs on survival due to limited data. We conclude that both local biotic and abiotic factors play important roles in determining seedling recruitment in this temperate forest.