Nonepileptic seizures (NES, psychogenic NES-PNES) are associated with significant morbidities. We evaluated the morbidities and mortality in a national group of children, adolescent, and adult patients before and after a first diagnosis of PNES. Methods: From the Danish National Patient Registry (1998–2013), we identified 1057 people of all ages with a diagnosis of NES and matched them with 2113 control individuals by age, gender, and geography. Comorbidities were calculated three years before and after diagnoses. Results: Patients with PNES showed increased comorbidities 3 years before and after diagnosis in almost all the diagnostic domains. The strongest associations were identified with other neurological diseases (after diagnosis, Hazard Ratio (HR): 38.63; 95% Confidence Interval (CI): 21.58–69.13; P < 0.001), abnormal clinical and laboratory findings (HR: 46.59; 95 CI: 27.30–79.52; P < 0.001), other health-related factors (HR: 12.83; 95%CI: 8.45–19.46; P < 0.001), and psychiatric comorbidities (HR: 15.45; 95% CI: 9.81–24.33). Epilepsy was identified in 8% of the patients with PNES. We found especially frequent comorbidity involving overweight, depression, anxiety, dissociative somatoform condition, other convulsions, lipothymias, reports of pain and other symptoms in several organ systems, and several reports of minimal traumas to the head, trunk, and extremities. Mortality was higher in patients with NES than in controls (HR: 3.21; 95% CI: 1.92–5.34; P < 0.001). Conclusion: Morbidity is more frequent in several domains, including neurological, psychiatric, and other diseases, before and after a diagnosis of NES. Mortality is significantly higher in patients with PNES as compared to controls.