Background: Bipolar disorder (BD) is associated with significant morbidity and mortality from metabolic diseases. There is a paucity of data regarding insulin resistance (IR) and its relationship with the metabolic syndrome (MS) in bipolar patients. Objective: To evaluate the prevalence of both IR and MS in BD outpatients and to assess clinical criteria associated with IR. Method: Cross-sectional study in 65 DSM-IV-TR BD patients consecutively assessed at the Bipolar Disorder Program at Hospital de Clínicas de Porto Alegre, Brazil. IR was diagnosed by the homeostatic model assessment – insulin resistance (HOMA-IR) and MS was diagnosed using three different definitions: National Cholesterol Educational Program – Adult Treatment Panel III (NCEP-ATP III); NCEP-ATP III modified criteria and International Diabetes Federation. Results: IR was present in 43.1% of the sample (women 40%, men 44.4%). The prevalence of MS defined by the NCEP-ATP III criteria was 32.3%, NCEP-ATP III modified was 40% and IDF was 41.5%. NCEP-ATP III modified criteria showed the best tradeoff between sensitivity (78.6%) and specificity (89.2%) to detect insulin resistance. Waist circumference was the clinical parameter most associated with IR. Discussion: Current MS criteria may provide reasonable sensitivity and specificity for the detection of IR in BD patients. Abdominal obesity is closely related to IR in this patient population.