The coronavirus disease 2019 pandemic had a major impact on most medical services. Our aim was to assess the outcome of acute cholecystitis during the nationwide lockdown period. All patients admitted to our emergency department for AC were analysed. Patient characteristics, performance status, AC severity, treatment modality and outcome of AC were assessed during the lockdown period (Period II: 1 April 2020–30 November 2021) and compared to a historical control period (Period I: 1 May 2017–31 December 2018). AC admissions increased by 72.8% in Period II. Patients were younger (70 vs. 74 years, p = 0.017) and greater in number in the CCI 1 group (20.4% vs. 11.2%, p = 0.043) in Period II. The unplanned readmission rate (6.3 vs. 0%, p = 0.004) and the gallbladder perforation (GP) rate was higher (18.0 vs. 7.3%, p = 0.006) in Period II. Percutaneous transhepatic gallbladder drainage (PTGBD) was more frequent (24.1 vs. 12.8%, p = 0.012) in Period II. In addition to a drop in patient age and CCI, a significant rise in the prevalence of acute cholecystitis, GP and unplanned readmissions was observed during the nationwide lockdown due to the COVID-19 pandemic. PTGBD was more frequent during this period, whereas successful conservative treatment was less frequent.