Patients with polycythemia vera (PV) are at increased risk of thrombosis and hemorrhages. Although hydroxyurea (HU) has been the frontline therapy for patients at high-risk of vascular complications, about 25% of patients develop resistance/intolerance to this therapy. The aim of this non-interventional, multicenter cohort study was to understand the clinical characteristics and HU treatment response of Portuguese PV patients. HU resistance/intolerance was defined according to adjusted European LeukemiaNet (ELN) criteria. 134 PV patients with a mean disease duration of 4.8±5.0 years were included and followed up for 2 years. At baseline, most patients were ≥60 years old (83.2%), at high risk for thrombotic events (87.2%), and receiving HU therapy (79.1%). A total of 10 thrombotic events and 8 hemorrhagic events were reported, resulting in a 5-year probability of thrombo-hemorrhagic events of 17.2%. Hematocrit (p=0.007), hemoglobin (p=0.012) and MPN10 symptom score (12.0±11.6 vs 10.3±9.1; p=0.041) decreased significantly at the 24-month visit compared to baseline. Overall, 75.9% of patients met at least one of the adjusted ELN criteria for HU resistance. 14.4% of patients remained on HU throughout the study. The results from this real-world study may help identify the subset of patients at higher risk of disease sequelae who may benefit from earlier second-line treatment.