Facial expressions act as a powerful readout device, influencing a viewer's own emotional response. Drawing from facial feedback theory, the mediating role of source expressive display-based judgments on the influence of source facial expressions on consumer attitudes toward advertising stimuli, attitudes toward endorsed brands, and behavioral intention is examined. In addition, the examination of expressive display-based judgments as an automatic phenomenon, contingent on the familiarity of the source and the perceived match with the product endorsed is investigated. Across three studies, the facial expression of a source (resting vs. smiling) is manipulated within endorsement contexts. Results demonstrate that when an endorser is pictured in an advertisement with a smiling facial expression, consumers report feeling more pleasant (pleasure), with this positive emotional response mediating the relationship between source expressive display and attitude toward an advertisement, attitude toward a brand, and purchase intention. Results also indicate that the emotional response derived from the presence of a smiling source in an advertisement occurs effortlessly, yet only for a familiar source and one that is perceived to match the product endorsed, indicating this process can be defined as automatic under certain conditions. The findings from these studies provide advertisers with an effective cue to enhance a consumer's emotional response to advertisements, which in turn heighten advertisement, brand, and behavioral based judgments.