Risk and time preferences have often been viewed as reflecting inherent traits such as impatience and self-control. Here, we offer an alternative perspective, arguing that they are flexible and environmentally informed. In Study 1, we investigated risk and time preferences among children in the United States, India, and Argentina, as well as forager-horticulturalist Shuar children in Amazonian Ecuador. We find striking cross-cultural differences in behavior: children in India, the United States, and Argentina are more risk-seeking and future-oriented, whereas Shuar children are more risk-averse and exhibit more heterogeneous time preferences, on average preferring more today choices. To explore 1 of the socioecological forces that may be shaping these preferences, in Study 2, we compared the behavior of more and less market-integrated Shuar children, finding that those in market-integrated regions are more future-oriented and risk-seeking. These findings indicate that cross-cultural differences in risk and time preferences can be traced into childhood and may be influenced by the local environment. More broadly, our results contribute to a growing understanding of plasticity and variation in the development of behavior. (PsycINFO Database Record (c) 2020 APA, all rights reserved).