The purpose of this study was to investigate the relationship between preschoolers' cognitive abilities and their fairness-related allocation behaviors in a dilemma of equity-efficiency conflict. In Experiment 1, 4- to 6-year-olds (N = 99) decided how to allocate five reward bells. In the first-party condition, preschoolers were asked to choose among giving more to self (self-advantageous inequity), wasting one bell (equity), or giving more to other (self-disadvantageous inequity); in the third-party condition, they chose either to allocate the extra bell to one of two equally deserving recipients or to waste it. Results showed that, compared with the pattern of decision in the third-party condition, preschoolers in the first-party condition were more likely to give the extra bell to other (self-disadvantaging behaviors) and that age, inhibitory control (IC), and theory of mind were positively correlated with their self-disadvantaging choices, but only IC mediated the relationship between age and self-disadvantaging behaviors. Experiment 2 (N = 41) showed that IC still predicted preschoolers' self-disadvantaging behaviors when they could choose only between equity and disadvantageous inequity. These results suggested that IC played a critical role in the implementation of self-disadvantaging behaviors when this required the control over selfishness and envy.