Background: As elective surgical services recover from the COVID-19 pandemic a movement towards day-case surgery may reduce waiting lists. However, evidence is needed to show that day-case surgery is safe for many ENT operations including endoscopic sinus surgery (ESS). We aimed to investigate the safety of ESS in England. Methods: This was an observational, secondary analysis of administrative data. Participants were all patients in England undergoing elective ESS procedure aged ≥ 17 years during for the five years from 1st April 2014 to 31st March 2019. The exposure variable was day-case or overnight stay. The primary outcome was emergency readmission within 30 days post-discharge. Results: Data were available for 49,223 patients operated on across 129 NHS hospital trusts. In trusts operating on more than 50 patients in the study period, rates of day-case surgery varied from 100% to 20.6%. Rates of day-case surgery increased from 64.0% in 2014/15 to 78.7% in 2018/19. Day-case patients had lower rates of 30-day emergency readmission (odds ratio 0.71, 95% confidence interval 0.62 to 0.81). For secondary outcomes measures, there was no evidence of poorer outcomes for day-case patients. Outcomes for patients operated on in trusts with ≥80% day-case rates compared to patients operated on in trusts with <50% rates of day-case surgery were similar. Conclusions: ESS can safely be performed as day-case surgery at current rates. There is a potential to increase rates of day-case ESS in England, especially in departments that currently have low rates of day-case ESS.