Rejection sensitivity (RS), the predisposition to defensively expect, readily perceive, and react strongly to interpersonal rejection (Downey & Feldman, 1996; Feldman & Downey, 1994), may be a transdiagnostic trait associated with a range of psychiatric symptoms and psychosocial dysfunction. Valid and reliable assessment of vulnerability factors is essential for individualized treatment and improving clinical outcomes. Limited research has examined the factor structure of the predominantly used self-report measure of RS, the Adult Rejection Sensitivity Questionnaire (A-RSQ; Berenson et al., 2009). Across two studies (Study 1: N = 346, 57.2% female, 76.6% White; 16.8% Hispanic/Latinx; Study 2: N = 540; 43.7% female, 80.2% White; 16.7% Hispanic/Latinx), we examined the factor structure of the A-RSQ in samples of adult U.S. residents and investigated associations with mental health correlates, including neuroticism, social anxiety, anxiety, depression, anhedonia, somatic arousal, and psychological distress. Study 2 also evaluated relations with interpersonal correlates, including introversion, submissiveness, and anxious and avoidant attachment. A two-factor solution with rejection expectancy and rejection concern representing separate factors consistently fit the data best. Distinct patterns of associations emerged suggesting that concern was more strongly associated with indicators of negative affect while expectancy was uniquely associated with diminished positive affect. Both concern and expectancy were associated with indicators of interpersonal dysfunction. Findings suggest that the current operationalization, and perhaps conceptualization, of RS as measured by the A-RSQ requires revision. Additionally, RS may be a clinically relevant transdiagnostic phenotype that influences symptom manifestation and psychosocial functioning. (PsycInfo Database Record (c) 2022 APA, all rights reserved).