Cognitive style is a major component of individuals' life history and everyday life. However, individual variations in cognitive styles are not well understood from an evolutionary functional perspective. Through two studies, we investigated how childhood unpredictability might be related to deliberate or intuitive cognitive styles. Study 1, in which we surveyed 301 undergraduate students, revealed that lower childhood unpredictability was a predictor of slower life-history strategies, and such strategies in turn predicted higher self-reported deliberate cognitive style. In Study 2 (N = 269), we experimentally manipulated mortality cues and subsequently assessed participants' deliberate responses by using the Cognitive Reflection Test. The results indicated that individuals who experienced higher childhood unpredictability, relative to those who had low childhood unpredictability, displayed a smaller proportion of deliberate responses when exposed to mortality cues but not when exposed to control cues. These results imply that childhood unpredictability might predispose individuals to specific cognitive styles that serve distinct adaptive functions. This is manifested as both long-term propensities in life-history development and short-term behavioral tendencies in threatening situations.