Aim: Most studies on the determinants of psychosocial functioning in first-episode psychosis used few predictors. This study examines the effects of multiple cognitive domains and multiple symptoms on psychosocial functioning. Methods: A total of 162 patients with a first-episode psychosis were assessed within 3 months after referral to an early psychosis treatment department. Four psychopathological subdomains (positive and negative symptoms, depression and anxiety) and five subdomains of psychosocial functioning (work/study, relationships, self-care, disturbing behaviour and general psychosocial functioning) were measured. Neurocognitive and social cognitive factors were identified through principal component analyses (PCA) of a 15-measure cognitive battery. Stepwise backward regression models were computed to identify the determinants of psychosocial functioning. Results: The three neurocognitive and four social cognitive factors identified through PCA were largely independent of psychopathology. The strongest associations were between cognitive factors and anxiety. Higher levels of negative symptoms, poor general neurocognition and poor general social cognition showed strongest associations with impaired psychosocial functioning, followed by low verbal processing speed and low emotion processing speed. Together, these factors accounted for 39.4% of the variance in psychosocial functioning. Conclusions: The results suggest that negative symptoms, impaired neurocognition and poor social cognition are related to psychosocial problems in patients with first-episode psychosis. None of the affective or positive symptoms had a marked impact on psychosocial functioning.