Gratitude has been regarded as a moral virtue in most cultures. This study examines how cultural differences may influence children's expression and understanding of gratitude. Two vignettes involving a high- and low-cost situation of expressing gratitude were presented to Japanese preschool-aged children, and their responses to the scenarios were recorded. Compared with the results of a previous study conducted with American children (Nelson et al., 2013), more Japanese children associated positive feelings with the benefactor when they were helped, would help the benefactor if they were in need, and cited reciprocity as a reason for doing so. The findings confirm the hypothesis that the emergence of gratitude as a moral virtue is also observed in preschool children from non-Western countries, and commonalities in moral development across cultures were found. At the same time, depending on the cost incurred by the benefactor on offering help, we found cultural differences in various aspects of gratitude. The findings suggest that gratitude, which encompasses the norm of reciprocity, is triggered in Japanese children in response to the cost to the benefactor.