Pheochromocytoma is a rare disease but frequently poses a diagnostic dilemma due to the unspecific symptoms and its potentially life-threatening nature. There is a perception of an increase in the incidence of pheocromocytomas in recent years, but no data on time trends exist. We obtained data from The Danish National Registry of Patients, The Danish Registry of Causes of Death, and The National Pathology Registry for all persons registered with pheochromocytoma in 1977–2015. Health records were reviewed to validate the diagnosis for all patients in the Northern and Central Regions of Denmark (population 1.75 million). Incidence rates were calculated using Poisson regression and time trends were analysed with year as a continuous explanatory variable. As incidence increased significantly in 2007–2015, we compared the clinical characteristics of patients diagnosed in this time interval with patients diagnosed in 1977–2006 in a secondary analysis using the Wilcoxon–Mann–Whitney test. We identified 183 confirmed cases of pheochromocytoma. A significant increasing trend (P<0.001) was observed in incidence rates from 2.06 (CI95% 1.68–2.49) per million person-years 1977–2006 to 4.65 (CI95% 3.72–5.82) 2007–2015. In 1977–2006 paroxysmal symptoms and secondary hypertension were the primary causes leading to the diagnosis (34 and 21%, respectively), while incidentalomas were the leading cause of diagnosis 2007–2015 (57%). Patients diagnosed 2007–2015 were older (P<0.001), less symptomatic (P=0.003) and had smaller tumours (P=0.033), compared to 1977–2006. No changes were observed in duration of symptoms or level of catecholamines. The incidence of pheochromocytoma has increased significantly in recent years, presumably due to increased use of imaging studies. It is unlikely that earlier diagnosis or lead-time bias accounts for the increasing incidence since patients are getting older. Therefore, these incidentaloma patients appear to represent a new group of pheochromocytomas not previously diagnosed. Whether surgical treatment provides a health benefit in this group remains unknown.