Given the high postural control demands of sport Jiu-Jitsu, prolonged training in this discipline may result in sport-specific adaptations, particularly in positions closely related to combat scenarios. This study aimed to evaluate the differences in reaction time and postural control between elite Jiu-Jitsu athletes and untrained individuals, highlighting the potential influence of specialized training on these critical performance attributes. This study was conducted on thirty-one young participants (fifteen Brazilian Jiu-Jitsu athletes and sixteen non-athletes). Reaction time was measured using the Fit Light Trainer system in two positions. Postural control was assessed during 30 s bipedal and single-leg standing, both with and without a dual task involving tracking a randomly moving point on a screen. Results indicated that athletes demonstrated significantly faster reaction times (p = 0.0242) and greater complexity in postural control mechanisms, as evidenced by higher fractal dimension values during single-leg standing with dual tasks in the anterior–posterior direction (p = 0.0011). These findings suggest that Brazilian Jiu-Jitsu athletes possess enhanced neuromuscular and cognitive–motor integration, crucial for managing the complex demands of martial arts. This study highlights the importance of incorporating dual-task scenarios in training to optimize athletic performance and postural control in high-demand sport contexts.