Magou Ndoye, of Senegal, has been living in Spain for almost 15 years, his lawyer said, but his application was rejected.
When people apply for Spanish citizenship, they must answer a series of questions demonstrating they have integrated into the society, The Local.es reported Wednesday.
The interview takes 10 minutes and involves 30 questions, and applicants must get a score of 27 or above.
Ndoye's lawyer, Marcelo Quilez Ochoa, said his client got most questions right, but did not know the name of Prime Minster Mariano Rajoy's wife, Elvira, as she keeps a low public profile.
The Ministry of Justice is currently reviewing the case.