Subclinical coronary artery calcification (CAC) is a risk factor for adverse cardiovascular events, but studies investigating its association with outcomes in hospitalized patients with COVID-19 are limited. This was a retrospective study of 457 patients without history of clinical coronary artery disease (CAD) who underwent chest CT imaging during COVID-19 hospitalization at MCW/Froedtert-affiliated hospitals from July 1, 2020 to July 1, 2021. Visually estimated CAC (yes/no) and CAC burden (none/mild/moderate/severe) were recorded from radiology reports. Unadjusted and adjusted regression models were used to assess associations between CAC and hospital length of stay (LOS), ICU admission, mechanical ventilation, and mortality. The mean age was 63.1 ± 15.3 years. Presence of CAC was associated with mechanical ventilation (p = 0.01), ICU admission (p = 0.02), in-hospital or 30-day mortality (p < 0.01), and hospital LOS (p < 0.001). Compared to no CAC, hospital LOS was increased for mild (p = 0.01) and severe CAC (p = 0.02) after adjustment for covariates. Severe CAC was also associated with increased ICU admission (OR 3.97; p = 0.002) and mechanical ventilation (OR 3.08; p = 0.03) after adjustment. In unadjusted analysis, in-hospital or 30-day mortality increased with magnitude of CAC severity, with HR 2.43 (p = 0.003) for mild and HR 3.70 (p = 0.002) for severe CAC. However, associations with mortality were not significant after adjustment. CAC is associated with increased ICU admission, mechanical ventilation, hospital LOS, and in-hospital or 30-day mortality for patients hospitalized with COVID-19. Patients with severe CAC, and without clinical history of CAD, represent a high-risk population for morbidity and mortality.