Extant evidence points toward the role of contextual information and related cross-cultural variations in emotion perception, but most of the work to date has focused on judgments of basic emotions. The current research examines how culture and situational context affect the interpretation of emotion displays, i.e. judgments of the extent to which ambiguous smiles communicate happiness versus polite intentions. We hypothesized that smiles associated with contexts implying happiness would be judged as conveying more positive feelings compared to smiles paired with contexts implying politeness or smiles presented without context. In line with existing research on cross-cultural variation in contextual influences, we also expected these effects to be larger in Japan than in the UK. In Study 1, British participants viewed non-Duchenne smiles presented on their own or paired with background scenes implying happiness or the need to be polite. Compared to face-only stimuli, happy contexts made smiles appear more genuine, whereas polite contexts led smiles to be seen as less genuine. Study 2 replicated this result using verbal vignettes, showing a similar pattern of contextual effects among British and Japanese participants. However, while the effects of vignettes describing happy situations was comparable in both cultures, the influence of vignettes describing polite situations was stronger in Japan than the UK. Together, the findings document the importance of context information in judging smile expressions and highlight the need to investigate how culture moderates such influences.