In the present studies we incorporate a Person × Situation perspective into the study of the persuasion source. Specifically, we aimed to identify the personality characteristics of the persuasive individual and test the moderating role of target and source involvement. In three studies we found support for hypothesized relationships between source persuasiveness and Extraversion, Neuroticism, and Openness to Experience, and evidence for a moderating effect of involvement. In a preliminary study (N = 66, Mage = 22.7, 64% female), we demonstrated expected differences in the personality ratings assigned to a hypothetical persuasive versus nonpersuasive individual. In Study 1 (N = 95, Mage = 24.1, 62% female), through sets of two-person debates, we showed that source Extraversion and Openness to Experience were positively, and Neuroticism negatively, associated with source persuasiveness. In Study 2 (N = 148, Mage = 24.3, 61% female), we manipulated the level of involvement and mostly replicated the results from Study 1, but, corresponding with our predictions, only when involvement was low. Our findings demonstrate the relevance of an interactionist approach to the study of persuasion, highlighting the role of personality in the study of the persuasion source.