The Cognitive Assessment Interview (CAI) is an interview-based instrument to assess cognition considering the impact of cognitive impairment on daily activities. We aimed to explore the associations of the Spanish version of the CAI (CAI-Sp) with a neuropsychological battery and a measure of psychosocial functioning in psychosis. The sample consisted of fifty-six first episode psychosis (FEP) patients and 66 non-FEP patients, who were assessed with a neuropsychological battery, the CAI-Sp and the Short Disability Schedule (DAS-S). Patients also underwent clinical assessment. Additionally, 37 controls were assessed with the neuropsychological battery and CAI-Sp, for normalization purposes. The results showed that CAI-Sp scores were overall correlated with the neuropsychological battery in non-FEP patients. In FEP patients, we found fewer significant correlations. Most associations were maintained after controlling for clinical symptoms. CAI-Sp rater scores contributed to the variance in the DAS-S scores in both groups, as did negative and disorganized symptoms. The CAI-Sp may be a good instrument to assess cognition in non-FEP patients. In FEP patients, it was less effective in capturing cognitive impairments and their functional consequences, probably because cognitive deficits have yet to become evident, due to the recency of illness onset, and no functional disturbances were observed due to these cognitive impairments.