The compatibility between partners in romantic relationships has been found for various characteristics, including intelligence. Theoretically, this phenomenon implies that people are able to discern the intelligence of themselves and others. In practice, however, the accuracy of such estimations is influenced by various factors, such as personality traits. Grandiose narcissism has been found to be the strongest personality predictor of self-overestimated intelligence, however, it remains to be determined whether the self-perceived bias generalises to people close to the narcissist, such as their romantic partners. In the current study, in a sample of 150 heterosexual couples, we examined whether grandiose narcissism was associated with self and partner's estimation of intelligence. Additionally, we measured participants' objective intelligence (Raven's test) and relationship satisfaction. First, we found that narcissism was associated with the overestimation of intelligence. Second, narcissistic women overestimated the intelligence of their partners. Furthermore, narcissistic women were perceived as highly intelligent by their partners, even after controlling for objective intelligence. Finally, we found support for assortative mating for narcissism. Thus, intelligence seems to be an important attribute in the way how narcissistic women perceive their partners, as well as how partners view the intelligence of narcissistic women.