Neurofibromatosis 1 (NF1) is a multisystem disease that can affect nearly every organ system. The aim of our study was to describe the in-hospital population with NF1 in France. We conducted a nationwide retrospective cohort study using the French hospital administrative database. A total of 11,425 patients with NF1 (53.4% female, 19,080 person years) were identified from January 2013 to December 2019. A total of 23% had at least one diagnosis of a comorbidity or NF1-associated complication or disease, and it was highest in the age group of 10-15 years. A total of 2,601 (22.8%) had a diagnosis of cancer. There were 366 (3.2%) in-hospital deaths, and we observed a standardized mortality ratio of 4.14 (95% confidence interval = 3.71-4.56), with a higher standardized mortality ratio in women and in the age group of 10-15 years. The standardized incident ratio (SIR) of cancer was 10.3 (95% confidence interval = 9.6-11.1). We observed high SIR values for cancer in childhood, with a decrease toward that of the general population by age 70 years. We observed high SIRs for NF1-associated cancers: CNS SIR of 195.4 (95% confidence interval = 172.2-220.9) and small intestine SIR of 102.9 (95% confidence interval = 71.7-143.2). The study provides a better understanding of the prognosis in people living with NF1.