While the objective level of intelligence is not associated with narcissism, relations to self-assessed intelligence (SAI) have been repeatedly reported. Existing research suggests that different facets of narcissism may have different associations with SAI. In the current daily diary study (N = 176; N = 3975 total observations), we employed dynamic structural equation modeling to examine the relationships between facets of trait and state narcissism (i.e., agentic, antagonistic, and neurotic) and the level, variability, and instability of SAI assessed over 28 consecutive days. Both trait and state narcissism were consistently related to SAI: agentic narcissism showed a positive relationship, whereas antagonistic and neurotic narcissism showed negative relationships with SAI. Trait agentic and state antagonistic narcissism predicted greater variability of SAI scores throughout the study, while neither trait nor state narcissism predicted the instability of SAI. Finally, we found that experiencing increased agentic narcissism on one day, predicted perceiving oneself as more intelligent on the next day, but feeling smarter did not predict feeling narcissistic over time. Moreover, we demonstrated that differentiating between narcissism facets yielded more theoretically accurate results compared to distinguishing between grandiose and vulnerable narcissism.