China’s rise and its consequences for U.S.-China relations and international stability has generated great scholarly interest. However, current research fails to explain why dominant powers such as the United States sometimes cooperates with rising threats like China. Edelstein notes that realists often conflate two types of uncertainty: risk, which one can assess using probabilistic estimates; and uncertainty, which suggests that, in complex world systems, outcomes are truly unknowable. We thus ask: do risk and uncertainty scenarios affect states’ strategic choices differently? Unlike offensive realists who argue uncertainty always increases conflictual possibilities because states fear the intentions of others, Edelstein following a defensive realist argument suggests that uncertainty rather than risk will enhance cooperation chances because when great powers are truly uncertain about rising powers’ intentions, they become less aggressive, preferring to wait and see. This paper adopts a survey experiment in China to evaluate how risk and uncertainty can encourage or reduce competitive state behaviors. Contradicting Edelstein, our experiment shows that uncertainty generates less chances for cooperation between dominant and rising powers than risk. In this vein, this paper serves as an empirical support to the offensive realist argument that portrays great power relations as invariably competitive affairs.