This study examined the association between sedentary behaviour and metabolic parameters among patients with schizophrenia. A total of 76 patients and 38 healthy age-, gender- and BMI-matched volunteers were included. Participants were asked for their overall sitting and physical activity behaviour using the International Physical Activity Questionnaire. Patients were additionally screened for psychiatric symptoms and extrapyramidal side-effects of antipsychotic medication. On average, patients with schizophrenia spent 8.5h per day sitting (versus 6.21h in healthy controls). Patients sitting more than 10.4h per day had a higher BMI, waist circumference and fasting glucose concentrations and experienced more negative and cognitive symptoms than those sitting less than 5.8h per day. Overall sitting time was associated with a significantly greater likelihood of metabolic syndrome. A stepwise backward-elimination multivariate regression analysis demonstrated that sitting time is a significant predictor for BMI. Current results suggest patients with schizophrenia may benefit from reducing total sitting time.