Background: Whether gastroparesis is associated with a shortened life expectancy remains uncertain as no systematic study has evaluated the impact of gastroparesis on mortality, based on gastric emptying (GE) tests. Aim: This study aimed to assess whether delayed GE was predictive of mortality. Methods: GE was measured using a 13C-octanoic acid breath test in 1563 consecutive patients. Delayed GE at baseline defined the gastroparesis group. Patients were followed up for a mean of 8.9 years, yielding 13 466 patients per year. Mortality was assessed using the French CepiDc database with data from local civil registries. The cause of death was determined from medical records. Mortality rates were assessed using the KaplanMeier method and hazard ratio (HR) was calculated using the Cox regression model. Results: Age and symptoms severity were not different among patients with normal GE (n = 1179) and with delayed GE (n = 384) while diabetes mellitus was more frequent in the gastroparesis group. Kaplan-Meier analysis showed increased mortality in the gastroparesis group compared to patients with normal GE. Cox regression model identified delayed GE as independently associated with increased mortality (HR = 1.63[1.09- 2.42]; P = 0.02). Other independent factors associated with increased mortality included age, male sex, and diabetes. No difference was observed between groups for the cause of death, with cancer and cardiovascular disease being the leading causes. Conclusion: This study has shown that gastroparesis, diagnosed on GE tests, was associated with increased mortality, independently of age, sex, BMI or diabetes status (NCT04918329).