Background: Since the beginning of COVID-19 pandemic, an increase in new diagnoses and pediatric hospital admission for anorexia nervosa (AN) or atypical AN in adolescents have been reported, suggesting an adverse effect of COVID-19 on youth mental health. We hypothesized possible differences in prevalence of hospitalization and/or disease severity, related to socio-economic status and/or ethnicity. Methods: Retrospectively, patients were divided into two subgroups and compared according to the date of first hospital admission: “pre SARS-COV2 era” group (n. 45, 8th March 2016–8th March 2020) and “SARS-COV2 era” group (n. 43, 9th March 2020–8th March 2022). Results: During the two years of the SARS-COV2 era, we reported an increase in hospital admission incidence more than doubled respect to the “pre-SARS-COV2 era”. The “SARS-COV2 era group” showed a more rapid weight loss (p = 0.005), a minor duration of weight loss from lifetime maximum to admission (p = 0.019) and needed most frequently treatments with intravenous fluids (p 0.0001), oral dietetic supplements (p 0.001) and enteral nutrition by nasogastric tube (p = 0.002). The same group presented higher prevalence of psychiatric comorbidities (63% vs. 22%, p 0.0001) and required most frequently treatments with psychotropic drugs (56% vs. 24%, p = 0.002). We found higher family socioeconomic status (SES) in our patients with AN in both the periods and we did not find a shift in social class distribution over time. Conclusions: Our study confirms a significant increase in incidence of hospitalization and of psychiatric comorbidity in the pediatric population with AN during the second year of COVID-19 pandemic, regardless of SES or ethnic background. Further studies are needed to understand potential mechanisms that during COVID-19 pandemic trigger eating disorder symptoms.