Wide empirical support exists for 2 aspects of narcissism-grandiosity and vulnerability. Hostility is a form of interpersonal antagonism, which is considered central to narcissism broadly. Though it has often been subsumed by the concept of narcissistic grandiosity, interpersonal antagonism is associated with vulnerability as well. Rejection represents an interpersonal stressor that evokes hostility to a greater degree in those high in narcissism, with mixed evidence regarding whether it stems from threat to one's egotism (grandiosity) or low self-esteem (vulnerability). Therefore, investigating the associations between narcissistic dimensions and individuals' trajectories of hostility leading up to and following rejection may provide a basis for a more unified conceptualization. In this study, we leverage the wide range of narcissistic expression displayed in a combined sample of borderline personality disorder (N = 56) and community (N = 60) individuals who completed ambulatory assessments approximately 6 times per day for 21 consecutive days. We examine whether narcissistic vulnerability and grandiosity, as measured by NEO Personality Inventory facet combinations constructed based on the Five-Factor Narcissism Inventory, moderate trajectories and overall levels of hostility surrounding self-reported interpersonal rejections. Grandiosity and vulnerability were independently positively associated with a faster rise in hostility leading up to rejection; however, greater grandiosity was uniquely associated with a greater spike in hostility at the occasion of rejection and subsequent faster recovery. These results are consistent with both the idea that grandiosity is proportionately more central to interpersonal antagonism and that antagonism serves as a bridge, connecting and reinforcing both narcissistic grandiosity and vulnerability. (PsycInfo Database Record (c) 2022 APA, all rights reserved).