This study investigated effects of seedling age and planting density on early growth performances of Fraxinus rhynchophylla trees. Containerized F. rhynchophylla seedlings (1-year-old and 2-year-old) were planted according to two different planting densities (3,000 and 5,000 trees ha-1) in April of 2017 in Gangneung city, Gangwon province, South Korea. Survival rate, root collar diameter (RCD), and height (H) were measured from 2017 to 2022 (except for 2021). H/RCD (H/D) ratio and stem volume were then calculated. It was found that growth performances of F. rhynchophylla trees were only affected by seedling age. In 2022, mean (±standard error) RCD (mm), H (cm), and stem volume (cm3 tree-1) were the highest for 5,000 trees ha-1 of 2-year-old seedlings (at 30.7, 197.3, and 1001.8, respectively). Initial RCD and H showed relationships with stem volume (in 2017- 2020). As growth space decreased, planted trees initially showed rapid growth due to light competition. In this study, the optimal seedling age and density of planting for F. rhynchophylla were confirmed and important data were secured for preparing a plan for post-reforestation management including operations of weed removal and young tree tending.