<p>How do people decide whom to help when information about others is limited? From an evolutionary perspective, personality traits may function as social cues that facilitate evaluations of potential interaction partners. The present study examined whether the Big Five traits of both potential helpers and targets predict helping intentions toward strangers. A total of 120 Japanese adults evaluated 40 experimentally constructed personality profiles and rated both their willingness to help and their liking for each target. Linear mixed-effects models revealed trait-specific patterns. Openness and extraversion showed no significant participant or target effects on helping intentions. In contrast, targets higher in conscientiousness and agreeableness received more help, and significant participant × target interactions emerged for both traits. Supplementary response surface analyses indicated that these interactions were not driven by personality similarity per se. Rather, individuals higher in conscientiousness or agreeableness were particularly responsive to the corresponding traits in targets. Additional mediation analyses showed that the interaction effects on helping were fully accounted for by liking, suggesting that personality traits influence helping primarily through evaluative processes. These findings indicate that agreeableness and conscientiousness function as socially interpretable cues that shape evaluations of potential partners under conditions of uncertainty. More broadly, the results suggest that social evaluation may represent a psychological mechanism through which personality traits contribute to assortative patterns in cooperation.</p>