Striving for more valid personality judgments is desirable as more sound decisions can be expected with increasing measurement accuracy. In this study, the psychometric qualities of the German HEXACO-60 personality inventory are evaluated. Extending previous studies, we examined the third-person observer-report form in addition to the first-person rating format, which allowed us to examine the psychometric quality beyond self-reports, such as cross-rater agreement, rank-order stability, structural validity, and measurement invariance. Data from 3,046 self-raters (61% female; age range: 14–90) and ratings from 2,199 well-informed acquaintances (partners, friends, or relatives of the self-raters) were analyzed. Satisfying internal consistency, 2-year and 4-year rank-order stabilities, agreement among self- and informant-raters, and consensus among informant-raters were found. Moreover, the six-factor structure was confirmed in structural equation models that incorporated the perspectives of both self-raters and informant-raters. Finally, partial strict measurement invariance was demonstrated across rater perspectives. Previous validation of the German HEXACO-60 self-report form could thus be replicated and expanded by highlighting the psychometric soundness of the third-person observer-report form and the convergent as well as discriminant validity of HEXACO trait measures across rater perspectives. The informant perspective provides valid additional benefits for the assessment of personality traits within the HEXACO framework.