We synthesize and discuss the available knowledge on the role of human cognition biases for sustainability and sustainable behavior. Human cognition biases are defined as any deviation in decision making from the standard framework of rational choice. We distinguish between biases in individual decision making and biases in group decision making, and highlight the relevance of each for sustainable behavior. We find that while both categories contribute to unsustainable behavior, human cognition biases in group settings are central to understanding many of the current sustainability issues. Moreover, we argue that the effects of group-related biases may outweigh those on the individual level in driving unsustainable behavior, and that biases that have been discussed under various labels in the literature can be interpreted as manifestations of human cognition biases in group settings.