Does nuclear weapon development embolden national leaders to engage in more assertive foreign policies? Despite the importance of this question to international security studies, the nuclear emboldenment hypothesis has received little attention. This article develops a theoretical explanation of emboldenment grounded in social psychology and uses translated archival sources and secondary studies to test it on the cases of Nikita Khrushchev and Mao Zedong. The results suggest that the dangers of nuclear emboldenment, while real, are substantially less than usually assumed. Biases associated with the availability heuristic cause leaders of new nuclear powers to authorize dangerous coercive policies in the short-term. However, the fear they experience at the nuclear brink causes them and their successors to authorize moderate policies in the longer-run. Findings achieved through case study analysis lead to the conclusion that nuclear proliferation is dangerous when leaders believe that nuclear coercion is safe, but becomes safe when they learn that nuclear coercion is dangerous.