The Sars-CoV-2 pandemic imposed unprecedented and drastic changes in health care organizations all over the world. To evaluate the impact of the pandemic on hospitalizations in an acute psychiatric ward. We retrospectively identified and compared acute psychiatric hospitalizations in the Service for Psychiatric Diagnosis and Care (SPDC) of AUSL-Modena during the pre-pandemic (n = 1858) and pandemic period (n = 1095), from 01/01/2017 to 31/12/2022. Data were statistically analyzed using STATA12. We collected 1858 hospitalizations in the pre-pandemic and 1095 in the pandemic. During the pandemic, we observed a progressively sharp reduction in voluntary hospitalizations, whereas involuntary ones remained stable with an increase in 2022 (p < 0.001), longer hospital stays (12.32 mean days vs 10.03; p < 0.001), longer periods of involuntary hospitalizations (8.45 mean days vs 5.72; p < 0.001), more frequent aggressive behaviour (16.10% vs 9.12%; p < 0.001) and referral to psychiatric communities at discharge (11.04% vs 6.13%; p < 0.001); non-Italians (p = 0.001), people with disability pension (p < 0.001) and Support Administrator (p < 0.001) were more frequently hospitalized. During the pandemic, voluntary psychiatric hospitalizations decreased, but not involuntary ones, and the most vulnerable people in serious clinical conditions were hospitalized.