Narcissism can manifest in a grandiose form - admiration-seeking, exhibitionism, and dominance - or a vulnerable form - anxiety, withdrawal, and hypersensitivity. While grandiose narcissism is conceptually in line with an independent self-construal, as prevalent in Western countries, the vulnerable form can be assumed to relate more to an interdependent self-construal, as prevalent in Eastern countries. We studied both forms of narcissism in Germany and Japan ( Ns = 258, 280), which differ fundamentally in their independent and interdependent self-construal, yet are similar regarding global developmental standards. We tested whether (1) mean differences in both narcissism forms would conform to the predominant self-construal, (2) self-construal would explain variance in narcissism beyond broad personality traits, and (3) there would be stronger mental health tradeoffs for culturally incongruent forms of narcissism. Our results largely confirm these expectations for vulnerable narcissism, which is (1) more prevalent in Japan than Germany, (2) related to self-construal beyond broad traits, and, (3) more strongly related to mental health problems in Germany than Japan. For grandiose narcissism, data analyses indicated that construct equivalence can only be assumed for the entitlement factor, and internal structure and nomological networks differ substantially between cultural contexts.