Objective This study examined the effect of social situations on risky decision-making in individuals with a borderline personality tendency (BT). Methods Fifty-eight participants with either high or low levels of BT were included in this study. Those who met the screening criteria were assigned to one of the two social situations (exclusion vs. inclusion) and they played the Cyberball game. Next, the participants were required to play the “Game of Dice” task to measure their decision-making pattern. Results The results revealed that individuals with high BT (n=28) showed significantly higher risky decision-making, compared with low BT (n=30) in the exclusion condition. However, no significant difference was found in the social inclusion condition. Conclusion In the social exclusion condition, individuals with high BT made risky decision in response to negative feedback, regardless of the previous decision. These findings can be applied to develop appropriate interventions in psychotherapy for individuals with borderline personality disorder/tendency.