A series of self-report measures of personality disorder from the perspective of the five-factor model (FFM) have been published; however, no informant-report versions have been developed. An informant version of the Five Factor Narcissism Inventory (FFNI) is particularly apt, given the degree of distortion in self-description inherent to narcissism. The present study provides initial validation for the Informant Five-Factor Narcissism Inventory (IFFNI). In Study 1, informant reports from friends, romantic partners, parents, and other family members were compared with self-reports provided by undergraduate college students on the IFFNI, FFM personality, and social dysfunction. Self–other agreement for IFFNI Grandiose (G) was higher than what has been found with other narcissism measures. No self-informant convergence, though, was found for IFFNI Vulnerable (V). From the informant view, IFFNI-G and V narcissism were associated with social dysfunction, whereas from the self-view only FFNI-V was associated with social dysfunction. In Study 2, grandiose and vulnerable narcissists, identified by participants recruited from MTurk, were described in terms of the IFFNI, FFM, and Pathological Narcissism Inventory (PNI). Results indicated that the IFFNI discriminated well between G and V narcissism for all but a few scales. The exceptions may reflect vulnerable narcissistic traits within grandiose narcissists. In comparison, the PNI obtained a very similar informant profile for the G and V narcissists. In sum, the results of the current study suggest value in having an informant-based measure of narcissism.