Introduction: Boxing performance is influenced by upper body strength, but the specific role of chest and back muscle strength in determining punching force remains unclear. This study examines the relationship between chest and back muscle strength and straight punching performance in elite amateur boxers. Methods: A cross-sectional design was employed, involving twenty Thai national amateur boxers who had participated in international competitions. Chest and back muscle strength were measured using the 1RM bench press and bench pull tests, with adjustments made for body weight. Punch force and related parameters for both jab and straight punches were assessed using force plates and motion capture equipment. Pearson's correlation coefficients were utilised to identify significant relationships between variables, with statistical significance set at p<0.05. Results: Chest muscle strength did not show significant correlations with jab frequency, velocity, or straight punch performance. However, both cumulative jab force (r=0.616, p=0.004) and jab punch force (r=0.761, p<0.001) were significantly correlated with chest muscle strength. No significant correlations were found between any of the punching performance metrics and back muscle strength. While no relationship was observed between the chest-to-back strength ratio and straight punch performance, notable positive correlations were identified with jab punch force and cumulative jab force. Discussion: The findings suggest that while straight punches rely on biomechanical factors such as trunk rotation and the transfer of force from the lower body, jab performance is influenced by chest muscle strength. Research indicates that a balanced chest-to-back strength ratio contributes to enhanced jab punch power. Trainers should ensure the proper balance of antagonist muscles and focus on developing chest strength for boxers who utilise jab techniques. Future biomechanical studies should explore the impact of neuromuscular coordination and lower limb involvement on straight punching mechanics.