Objective Schizophrenia is associated with reduced cardio-respiratory fitness (CRF), and impaired cognition is a core feature of the disorder. Despite their particular significance to schizophrenia disparately, the relationship between these two variables has not yet been thoroughly assessed. In this study we aimed to investigate naturally occurring associations between CRF and all cognitive domains within this patient population. Method Eighty outpatients with schizophrenia spectrum disorders participated in the study. Neurocognition was assessed with the Wechsler Adult Intelligence Scale version 4 General Ability Index (WAIS GAI) and the MATRICS Consensus Cognitive Battery (MCCB). Oxygen uptake was measured directly by analyzing O2 and CO2 content in expired air during a maximum exercise session on a treadmill using a modified Balke protocol. Clinical symptom load was assessed with the Positive and Negative Syndrome Scale (PANSS). Hierarchical multiple regression analyses were conducted, controlling for sex and age, and negative psychotic symptom levels. Results CRF explained a significant 8.2% and 9.1% of the variance in general intellectual ability and state-sensitive cognitive functioning respectively, beyond the impact of negative psychotic symptom load. Conclusion The study indicates a direct relation between CRF and cognition in schizophrenia. Impaired cognition is a difficult-to-treat expression of the disorder, and identifying modifiable factors possibly mediating cognition, such as CRF, is of great clinical value.