<p>A smile plays an essential role in human cooperation and affiliation, being the most used facial expression in interpersonal relationships. It is also documented that the judgment of facial expressions is influenced by our knowledge of the person and the associated context. While many studies have documented the influence of external contexts (e.g., odors, visual cues), few have examined the influence of internal factors, such as the characteristics of the smiler (e.g., smiler’s cognitive abilities) on the perceived sincerity of the smile. This study examines how the description of the personality of a person smiling influences the judgment of their smile’s sincerity. Participants (<i>n</i> = 200) read short paragraphs providing context about a smiler’s personality traits, based on the HEXACO model, including honesty humility, emotionality, extraversion, agreeableness, conscientiousness, and openness to experience. Half of the descriptions were positive and half were negative. Participants then assessed the sincerity of Duchenne and non-Duchenne smiles and were instructed to focus solely on the smile and ignore the context. Participants’ own personality traits were assessed using the HEXACO-60 questionnaire. Results indicate that Duchenne smiles are rated significantly more sincere than non-Duchenne smiles. Smiles contextualized with positive trait descriptions are perceived as more sincere than those associated with negative traits. Furthermore, traits provided about the smiler such as honesty-humility significantly influence sincerity judgments, being rated as most highly sincere in positive contexts and the least sincere in negative contexts. Participant personality traits did not significantly predict smile sincerity judgments in linear analyses, but a VSURF feature selection analysis did identify some traits as predictive, suggesting possible non-linear or interactive effects for these variables.</p>