PurposeSmiles displayed at varying intensities by service providers may result in different social judgments by customers, affecting decision-making. This study investigates the joint effect of customers' sense of power (low vs. high) and service providers' smile intensity (slight vs. broad) on their warmth and competence perceptions in service encounters.Design/methodology/approachThe authors conducted four experiments based on the Stereotype Content Model (SCM) of social judgments and the agentic-communal model of power, and assessed the impact of perceived power and smile intensity in different service encounter contexts.FindingsThe interaction effect of customers' sense of power (low vs. high) and service providers' smile intensity (slight vs. broad) influences customers' social judgments (warmth perceptions vs. competence perceptions). A service provider who displays a broad smile is more likely to be perceived as warmer by customers with a low sense of power, but less competent by those with a high sense of power. Furthermore, mediation analysis revealed that the combined effect of customers' sense of power and service providers' smile intensity on customers' subjective well-being and purchase intentions might be attributed to their social judgments.Originality/valueThis study reveals the intrinsic mechanism behind the interaction effect between smile intensity and sense of power affecting customers' purchase intentions and subjective well-being, namely, warmth/competence perceptions.