‘Jumping to conclusions’ (JTC) is a reasoning bias consisting of a tendency to take a decision without having enough information about an event. It has been related to the presence of delusions. The aim of the present study was to assess the relationship between three tasks differing in complexity and concept which assess JTC and cognitive functioning in a sample of people with schizophrenia and healthy participants. We also assessed which cognitive variables, after controlling for psychotic symptoms, explained the presence of JTC in each sample. A total of 43 patients with schizophrenia and 57 healthy participants were assessed with a cognition battery including executive function, verbal memory, and IQ. JTC was assessed with three tasks (probability of 85:15; 60:40, and 60:40 with emotional component). Patients were also assessed on psychotic and affective symptoms and the healthy participants on proneness to hallucinations and delusion. The present study demonstrates a clear relationship between JTC and cognitive functioning, especially in working memory, verbal memory, and cognitive processing speed in people with schizophrenia and in healthy participants. However no relationship was found in the emotional task of JTC. Hallucinations (in people with schizophrenia) and proneness to hallucinations (in the healthy participants) are related to JTC. Our results suggest that diverse psychological interventions such as cognitive remediation, cognitive behavioral therapy and meta-cognitive training might contribute to reducing JTC bias.