Objectives. This study investigated whether Sasang constitutional type is associated with differences in the serum levels of stress hormones and oxidative stress. Methods. A total of 236 participants (77 males and 159 females) were enrolled. The serum levels of cortisol, adrenaline, reactive oxygen species (ROS), and malondialdehyde (MDA) were analyzed. Results. The distribution of Sasang constitutional types was as follows: Taeumin, 35.6%; Soumin, 33.0%; and Soyangin, 31.4%. The serum cortisol levels of Taeumin were significantly lower than Soumin (p<0.1 in both sexes) and Soyangin (p<0.05 in males and p<0.1 in females). The adrenaline levels were also significantly lower in Taeumin than in Soumin (p<0.05 in males and p<0.1 in females) and Soyangin (p<0.1 in males). Serum ROS levels were significantly higher in Soyangin than in Taeumin and Soumin (p<0.05 in males), whereas MDA levels were significantly lower in Taeumin compared with Soumin and Soyangin (p<0.05 in males and p<0.1 in females). Conclusion. Taeumin type may tolerate psychological or oxidative stress better than other types, which suggests a biological mechanism to explain the different pathophysiological features of Sasang constitutional types.