Subtle social cognitive deficits in unaffected relatives of schizophrenia patients have received increasing attention over the last few years, supporting their potential endophenotypic role for this disorder. The current study assessed non-psychotic first-degree relatives' performance on a multidimensional measure of emotional intelligence (EI): the Mayer–Salovey–Caruso Emotional Intelligence Test 2.0 (MSCEIT). Endorsed by the National Institute of Mental Health, the MSCEIT is a valid and reliable instrument for detecting emotion-processing deficits among schizophrenia patients and people high in schizotypy. Method: Thirty-seven first-degree relatives, 37 schizophrenia outpatients and 37 healthy controls completed the MSCEIT, which comprises eight subscales aimed to assess the four branches of EI: Identifying, Facilitating, Understanding and Managing Emotions. Potential associations with cognitive function and schizotypy levels, measured with the Schizotypal Personality Questionnaire–Brief, were further evaluated. Results: Relatives had significantly lower MSCEIT total scores than controls and also significantly lower scores on the Identifying emotions branch. Nevertheless, schizophrenia patients still had the poorest global EI performance. The strongest positive correlations were found in relatives and controls with measures of executive function, processing speed and general intelligence. A higher level of schizotypy correlated significantly with lower MSCEIT scores among controls, but not among relatives. Conclusions: Contrary to expectations in the general population, the current study observed subtle EI impairment in non-psychotic first-degree relatives of schizophrenia patients. These findings support the hypothesis that these EI deficiencies may be potential endophenotypes located between the clinical phenotype and the genetic predisposition for schizophrenia.