Personality traits relate to risk for psychopathology and can inform predictions about treatment outcome. In an effort to obtain a comprehensive index of personality, informant reports of personality are sometimes obtained in addition to self‐reports of personality. However, there is limited research comparing the validity of self‐ and informant reports of personality, particularly among those with internalizing psychopathology. This is important given that informants may provide an additional (and perhaps different) perspective on individuals’ personality. The present study therefore compared how both reports of positive affectivity (PA) and negative affectivity (NA) relate to psychophysiological and subjective measures of emotional responding to positive and negative stimuli. Given that our sample (n = 117) included individuals with no history of psychopathology, as well as individuals with major depressive disorder (MDD) and/or panic disorder (PD), we were also able to explore whether these internalizing diagnoses moderated the association between personality reports and measures of emotional responding. Informant‐reported PA predicted physiological responses to positive stimuli (but not negative). Informant‐reported NA predicted physiological responses to negative stimuli (but not positive). Self‐reported personality did not predict physiological responding, but did predict subjectively measured emotional responding (NA for negative responding, PA for positive responding). Diagnoses of internalizing psychopathology (PD or MDD) did not moderate these associations. Results suggest self‐ and informant reports of personality may each provide valid indices of an individual's emotional response tendencies, but predict different aspects of those tendencies.