Introduction. The need for efficient training programs is critical for high-performance in competitive soccer. High- -intensity interval training is an effective exercise modality that can improve both the aerobic and anaerobic energy systems, but its efficacy to enhance performance-related tests in well- -trained soccer players is unknown. Aim of Study. The purpose of this study was to evaluate a bodyweight high-intensity interval training program and its effects on critical velocity via a 50-meter 3-minute all-out test and maximal sprint speed by a 40-yard dash in well-trained soccer players during the competitive season. Material and Methods. The experimental subjects performed a progressive series of high-intensity exercises and conditioning, twice per week for 4 consecutive weeks, in addition to their regular practice and match schedules. A 2 × 2 ANOVA was used for both performance tests, along with the smallest worthwhile change and smallest real difference to measure practical significance compared to the athletes who did not perform the additional training protocol. Results. No statistically significant differences were found between time or groups for the 40-yard dash (p = 0.079; p = 0.161) or 50-m 3-minute all-out tests (p = 0.052; p = 0.351), however, significant small (p = 0.024) and trivial (p = 0.04) interactions were found, respectively. For practical significance, considerable differences between the experimental and control groups were found for both performance tests. Conclusions. The results can be a practical option for strength and conditioning coaches to improve game-impacting sprinting and critical velocity in well-trained soccer players within a 4-week in-season training period with minimal additional training investments.