Background: Poor balance ability is a predictor of injuries of the lower extremity. Multi-intervention proprioception preventive programs, comprising balance training, strength, plyometric, agility, running, and stretching exercises, are effective in improving balance ability and reducing the risk of lower extremity injuries in athletes. Objective: The aim of the study was to examine the effect of a 20-week in-season multi-intervention proprioceptive neuromuscular training program on postural stability in male youth basketball players. Methods: Twenty-one elite male youth basketball players were divided into an intervention group (n = 10, age 17.3 ± 1.3 years) and a control group (n = 11, age 16.5 ± 1.8 years). During the in-season period (20 weeks), the intervention group followed a proprioceptive and neuromuscular training program, three times per week and 20 minutes per session. Balance was tested in a quiet unipedal stance (on both the dominant and non-dominant leg) on a foam mat with eyes open, before and after a 20-week period in both groups. The mean velocities in the medial-lateral and anterior-posterior directions and the mean total velocity of the centre of pressure (COP) displacement were obtained with a force platform. Results: The combined effect (pre-post test × group) showed that intervention resulted in significant improvement in the mean COP velocity for both the dominant and non-dominant limb in the anterior-posterior direction (p = .013 and p < .001, respectively) and in the medial-lateral direction (p = .007 and p < .001, respectively) as well as in the total COP velocity (p = .009 and p < .001, respectively). Conclusions: The specific proprioceptive and neuromuscular training had a positive effect on postural stability for both the dominant and non-dominant limb in basketball players.