Wearable passive resistance devices have emerged as potential tools for enhancing athletic performance without disrupting natural biomechanics. This study investigated the acute biomechanical impact of a novel passive exosuit designed to assist torso rotation and enhance clubhead speed (CHS). Twelve skilled golfers performed swings under two conditions:​ normal and exosuit-assisted. Compared to the normal condition, CHS significantly increased by 2.55 % (P = 0.009) when wearing the exosuit, rising from 43.3 ± 3.8 m/s to 44.4 ± 4.0 m/s. Although no significant differences were observed in X-factor at the top of the backswing, maximum X-factor, X-factor stretch, or maximum rate of X-factor stretch (MROS), the maximum rate of X-factor recoil (MROR) was significantly higher with the exosuit (P = 0.03), indicating enhanced rotational recoil during the downswing. Mechanical work analysis revealed a significantly greater total negative work during the backswing (P = 0.04) and a higher total positive work during the downswing (P = 0.03) in the transverse plane during swings with the exosuit, reflecting enhanced energy storage and return. These findings suggest that the current passive exosuit improves golf swing performance by augmenting rotational dynamics in the transverse plane without altering swing kinematics. This offers practical applications for performance training and biomechanical optimization in golf.