Inequality has been linked with many negative consequences for both societies and individuals. The harmful effects of perceived inequality operate at the individual level through the experience of personal relative deprivation leading to psychosocial stress. We examined if feelings of personal relative deprivation were related to participation in group decision-making, and predicted that greater feelings of deprivation would be related to less participation. That is, deprived individuals would assess others as having greater ability/opportunity to contribute (i.e. lower cost) and as a result would down-regulate their (potentially high cost) contributions within the group. We examined the relationship between relative deprivation and group participation in a simulated high-pressure hypothetical scenario. Students (N = 192) in groups of 6 had to come to a consensus decision despite being assigned roles with competing interests. Results indicate that relative deprivation predicted 9% of variance in exercise participation over and above demographic and situation-related variables (e.g. stress, competition, agreement with role), such that more relative deprivation was related to less participation. The overall regression model accounted for 58% of variance in participation. These findings suggest that negative social comparisons related to inequality have critical implications for group-based decision making and small group dynamics.