Poor social skills and abnormal behaviors are key features of schizophrenia and comprise important aspects of social functioning. Previous studies have shown that impairment of a social cognitive capacity for mental state attribution may be predictive of poor social skills. Poor social skills also seem to be related to the presence of negative symptoms, whereas the association with other symptom domains seems less clear. The contribution of nonsocial cognition, particularly executive functioning, to functional outcome in schizophrenia, and the relationships between social and nonsocial cognition, continue to be debated. To examine the relationships of mental state attribution with social skills, neurocognition and clinical symptomatology, we pooled data from two previous independent studies into one sample of 69 patients with schizophrenia. The sample was stratified for IQ, age range, and attention deficits. We also used a novel five-factor model of the Positive and Negative Syndrome Scale. A combined verbal and non-verbal score of mental state attribution was the best cognitive predictor of social skills, whereas neurocognition (i.e., executive planning skills) did not mediate this effect. When measures of psychopathology were included, levels of disorganized and negative symptoms predicted large proportions of variance in social functioning. Nevertheless, mental state attribution remained the sole, significant cognitive predictor variable in the equation. In conclusion, a capacity for mental state attribution is uniquely important for social skills in schizophrenia. As such, training to target social cognitive skills, including mental state attribution, may be particularly beneficial for patients' social functioning.