Negative symptoms and poor cognition are both associated with poor functional outcome in schizophrenia. This poor functional outcome has been attributed to poor cognition rather than any independent contribution from symptoms. Identifying target cognitive processes and mechanisms that predict community function, and possible moderator effects of negative symptoms, will allow the development of cognitive remediation programs that are successful in improving functional outcome. A referred sample of 53 in- and outpatients with schizophrenia with general cognitive impairment (including 28 with severe negative symptoms) and 22 healthy controls, balanced for premorbid IQ, were compared cross sectionally on measures of community shopping skills, executive function, and working memory. Across the groups, there were direct relationships between community functioning and specific executive functions, and there were interactions between group membership and the types of associations found. Working memory was independently associated with accurate community functioning only in people with schizophrenia and negative symptoms. This association was not due to the sole presence of working memory impairment or just to negative symptoms. Poor community function is predicted both by specific cognitive impairments that are prominent in people with negative symptoms and through the moderating effect of negative symptoms on the working memory-community function relationship. This may reflect a synergistic association between symptoms and cognition: negative symptoms arise from cognitive impairment but also impact detrimentally on working memory functioning. Both cognitive processes and negative symptoms should be targeted in cognitive remediation to effect the greatest change in community functions.