Purpose: This research aims to examine the effect of spokesperson facial symmetry on advertisement attitude, brand attitude and purchase intention and the mediating role of source authenticity on attitudinal and behavioral judgments. Design/methodology/approach: Two studies were undertaken. Study 1 examined the effect of facial symmetry on source authenticity and endorsement effectiveness. Study 2 investigated the influence of the authentic facial cues of freckles and moles on source authenticity and advertisement attitude, brand attitude and purchase intention. Findings: Findings indicate that source authenticity is the mechanism that explains attitudinal and behavioral judgments toward advertisements featuring asymmetrical spokespeople. The phenomenon observed is due to a proposed source authenticity overgeneralization effect, whereby spokespeople with asymmetrical faces are perceived as more genuine and real which, subsequently, results in more positive attitude toward the advertisement, attitude toward the brand and greater purchase intention than advertisements featuring spokespeople with symmetrical faces. The addition of authentic (biological) facial cues (i.e. freckles and moles) on spokespeople with a symmetrical facial structure, however, can heighten perceptions of source authenticity and the manifestation of the source authenticity overgeneralization effect. Research limitations/implications: This research has implications for marketing managers in the selection and depiction of spokespeople in their advertisements. However, this research is limited, as it only examines the facial feature characteristics of symmetry, freckles, and moles. Originality/value: This research shows that an asymmetrical facial structure can positively influence source, attitudinal and behavioral judgments. This research also identifies that although symmetrical facial structures dilute source- and endorsement-based judgments, the addition of authentic facial cues, freckles and moles, can reverse the negative effects and enhance perceptions of source authenticity, attitude toward the advertisement, attitude toward the brand and purchase intentions.