PURPOSE/BACKGROUND: Trunk exercises, such as trunk stabilization exercises (SE) and conventional trunk exercises (CE), are performed to improve static or dynamic balance. Recently, trunk exercises have also been often used as part of warm-up programs. A few studies have demonstrated the immediate effects of SE and CE on static balance. However, immediate effects on dynamic balance are not yet known. Therefore, the purpose of this study was to compare the immediate effect of SE with that of CE on the Star Excursion Balance Test (SEBT). METHODS: Eleven adolescent male soccer players (17.9 ± 0.3 years, 168.5 ± 5.4 cm, and 60.1 ± 5.1 kg) participated in this study. A crossover design was used, and each participant completed three kinds of testing sessions: SE, CE, and non-exercise (NE). Experiments took place for three weeks with three testing sessions, and a 1-week interval was provided between different conditions. Each testing session consisted of three steps: pretest, intervention, and posttest. To assess dynamic balance, the SEBT score in the anterior, posteromedial, and posterolateral directions was measured before and 5 minutes after each intervention program. The data of reach distance were normalized with the leg length to exclude the influence of the leg length on the analysis. RESULTS: The SEBT composite score was significantly improved after the SE (p < 0.05) but did not change after the CE and NE (p > 0.05). Furthermore, in the SE condition, SEBT scores of the posterolateral and posteromedial directions were significantly improved at the posttest, compared with those at the pretest (p < 0.05). CONCLUSIONS: This study demonstrated the immediate improvements in the posteromedial and posterolateral directions of the SEBT only after the SE. This result suggests that the SE used in this study is effective in immediately improving dynamic balance. LEVELS OF EVIDENCE: 3b.