Positive uncertainty refers to uncertainty surrounding an anticipated positive outcome. It provides consumers with the opportunity to imagine and speculate on a product's or experience's potentially positive characteristics. Research has shown that when uncertainty is associated with something positive, consumers may prefer uncertainty to certainty. In a between-subjects experimental design with a large US (n = 446) and Japanese sample (n = 453), the present study demonstrates that positive uncertainty increases consumers' positive feelings when they evaluate a product, particularly for high-involvement products that allow consumers to imagine and speculate about potentially positive product benefits. Unexpectedly, the study findings are consistent across the two different markets, which vary substantially in terms of consumers' level of uncertainty avoidance. Specifically, results show that future-framed advertisements are effective in generating positive uncertainty and that positive uncertainty generates positive attitudes, both in countries scoring high (Japan) and low (USA) on uncertainty avoidance.