Background The diagnosis of idiopathic pulmonary fibrosis (IPF) is often delayed up to several years. The objective of this study was to assess the impact of the diagnostic delay on progression-free survival, quality of life and hospitalisation rates. Methods A total of 264 incident patients with IPF were included immediately after their diagnosis and followed for up to 5 years, with regular collection of clinical data, quality-of-life questionnaires and assessment of disease progression. Hospitalisation data were extracted from electronic patient records. Analyses were performed on the entire cohort and strata according to forced vital capacity (FVC) at diagnosis. Results A long diagnostic delay (>1 year) was associated with worse progression-free survival compared with a short diagnostic delay (<1 year) (HR: 1.70, 95% CI: 1.18 to 2.46, p=0.004) especially in patients with mild disease at the time of diagnosis (FVC>80% predicted). Mean total scores of the St. George's respiratory questionnaire (SGRQ), a derived IPF-specific version of the SGRQ and the chronic obstructive pulmonary disease assessment test (CAT) were consistently higher in patients with long diagnostic delays, indicating worse quality of life. Mean hospitalisation rates were higher during the first year after diagnosis (Incidence rate ratio [IRR]: 3.28, 95% CI: 1.35 to 8.55, p=0.01) and during the entire follow-up (IRR: 1.74, 95% CI: 1.01 to 3.02, p=0.04). Conclusion A diagnostic delay of more than 1 year negatively impacts progression-free survival, quality of life and hospitalisation rates in patients with IPF. These findings highlight the importance of an early diagnosis for proper management of IPF. Trial registration number NCT02755441.