Introduction: Pheochromocytoma and catecholamine-secreting paraganglioma (PPGL) are rare, but potentially life-threatening tumors. We aimed to create a national cohort of incident PPGL patients by linking data from the national health registries for later studies on the morbidity and mortality of PPGL. Patients and methods: We obtained data from the Danish National Registry of Patients, the National Pathology Registry and the Danish Registry of Causes of Death for all persons registered with pheochromocytoma or catecholamine-hypersecretion in Denmark 1977-2016. We then reviewed health records for all persons living in the North and Central Regions of Denmark to validate the diagnosis of PPGL. We tested a number of algorithms for accurately identifying true cases of PPGL to maximize positive predictive values (PPV) and completeness. The best algorithm was validated in an external sample of 110 algorithm-positive patients. Results: We identified 2626 persons with a PPGL diagnosis code in Denmark, including 787 (30.0%) in North and Central Denmark. We retrieved the health records of 771⁄787 (98.0%) persons and confirmed 198 incident PPGL patients (25.3%). By combining patterns of registrations, we created an algorithm with a PPV for PPGL of 93.1% (CI95%: 88.5-96.3) and completeness of 88.9% (CI95%: 83.7-92.9), thus creating a national PPGL cohort of 587 patients. PPV for the optimal algorithm was 94.3% (CI95%: 87.1-98.1) in the external validation sample. Conclusion: Diagnosis codes for pheochromocytoma had a low validity in several individual health registries. However, with a combination of registries we could identify a near-complete national cohort of PPGL patients in Denmark, as a valuable source for epidemiological research.