AbstractMost studies have treated grandiose narcissism as a unidimensional construct and investigated its associations in cross-sectional convenience samples. The present research systematically addresses these limitations by investigating the associations of agentic and antagonistic aspects of narcissism in the interpersonal, intrapersonal, and institutional domains, cross-sectionally and longitudinally in a population-representative sample. We used data (N = 1,526) from the representative, longitudinal German Socio-economic Panel study innovation sample (SOEP-IS). Both pre-registered and exploratory research questions regarding interpersonal, intrapersonal, and institutional outcomes of agentic and antagonistic aspects of narcissism were tested. Cross-sectional associations generally confirmed the differential adaptivity of narcissism aspects: While agentic narcissism was related to friendship, happiness, self-esteem, employment, leadership and income, antagonistic narcissism was negatively related to intrapsychic adjustment. Longitudinally, agentic aspects were positively associated with holding a leadership position while the antagonistic aspects were related to lower self-esteem and being unemployed. Additional differentiated longitudinal associations were found for different age groups with most associations being more pronounced in middle adulthood. The present research highlights the importance of studying grandiose narcissism as a two-dimensional construct, in populations that are diverse and representative of the broader population, and with outcomes relevant to the population studied.