This study examined the characteristics, such as muscle power and agility, of top-level junior soft tennis players. 36 Japanese top-level junior (under-14) boys soft tennis players (age 13.4 ± 0.8 years, height 165.0 ± 9.7cm, and weight 53.9 ± 11.1 kg) with experience in international meet participation and 25 junior boys soft tennis players (age 13.1 ± 0.7 years, height 158.2 ± 9.5cm, weight 47.0 ± 8.2 kg) with experience in prefectural meet participation were the subjects of this study. Medicine ball (2 kg) throws to the right or left by trunk rotation and forward and backward by trunk extension (exercises recommended by Japan's soft tennis association) were selected to evaluate the muscle power of the subjects. Side step, spider, and front-back shuttle run tests (used by an American tennis association) were selected to test the agility of the subjects. The top-level athletes were significantly superior to the other junior players in the forward medicine ball throw, side step, and spider tests. These results suggest that muscle power in the forward direction and agility when moving to the right, left or diagonal direction are more developed in top-level soft tennis players than in other players.