Perfectionistic self-presentation is proposed as a deleterious interpersonal style that has an influence in clinical contexts that involves promoting a public image of perfection and avoiding displays and self-disclosures of imperfections. A sample of 90 clinical patients taking part in a clinical interview were assessed in terms of their levels of perfectionistic self-presentation and trait perfectionism and their affective, cognitive, and physiological reactions. Perfectionistic self-presentation dimensions were associated with (1) greater distress before and after the interview, (2) negative expectations and greater threat prior to the interview, and (3) post-interview dissatisfaction. Analyses of physiological data found that perfectionistic self-presentation was associated with higher levels of heart rate when discussing past mistakes, and, as expected, the need to avoid disclosing imperfections predicted higher levels of and greater change in heart rate when discussing past mistakes. Analyses that controlled for trait perfectionism and emotional distress showed that the need to avoid disclosing imperfections was a unique predictor of (1) appraisals of the interviewer as threatening before the interview and as dissatisfied after the interview; (2) negative pre and post self-evaluations of performance; and (3) greater change in heart rate when discussing mistakes. Perfectionistic self-presentation is discussed as an interpersonal style that can influence therapeutic alliance and treatment success.