The dynamic strength index (DSI) is calculated as the ratio between countermovement jump (CMJ) peak force and isometric mid-thigh pull (IMTP) peak force and is said to inform whether ballistic or strength training is warranted for a given athlete. This study assessed the impact of an individualized in-season resistance training program, guided by DSI on basketball players’ physical performance. Forty-three elite players (19.4 ± 2.9 years; 1.97 ± 0.08 cm; 89.1 ± 9.5 kg) were divided into an intervention group (IG) (27 players) and a control group (CG) (16 players). The IG was further split based on DSI into a ballistic group (DSI ≤ 0.90, 11 players) and a strength group (DSI > 0.90, 16 players). Over five weeks, participants underwent two weekly resistance sessions, with the IG following a DSI-based program and the CG a standard program. Performance was measured pre- and post-intervention through 20-m sprints, 505 change of direction test, CMJ, and IMTP. There were statistically significant improvements in the IG, notably in sprint times (η2 = 0.12-0.21, p < 0.05) and 505 test (η2 = 0.15-0.16, p < 0.05), predominantly in the strength group. The CG’s performance was either unchanged or declined for different variables. Our results suggest that DSI-guided training effectively enhances basketball players’ physical performance within a competitive season.

• Evaluating DSI and programming based on DSI values is an efficient way to enhance basketball players’ physical performance within a competitive season.

• Individualized training consisted of three exercises of three sets, performed twice a week is sufficient to improve (or prevent a decrease in) the physical performance of basketball players during the basketball season.

• An average DSI value of 0.9 indicates that basketball players are largely velocity/ballistic dominant athletes, thus strength training may be the preferable option during the basketball season for improving physical performance if individualization is not possible.

• The uniqueness of this study is that it was conducted at a high level of basketball during the competitive season, thus the findings of these studies are ecologically valid, with the methods being easily applied by coaches for programming to improve the physical performance of basketball players during the tapering phase before the post-season.