Background Studies have shown that COVID-19 could lead coagulation defects, resulting in increased morbidity and mortality. In this study, we sought to estimate the prevalence of deep vein thrombosis (DVT) among COVID-19 hospitalizations and its effects on hospital outcomes using a large administrative database. Methods We conducted a retrospective analysis of the 2020 California State Inpatient Database. All hospitalizations ≥18 years and primary diagnosis of COVID-19 were included and were stratified into those with and without DVT. The main outcomes of the study were in-hospital mortality, prolonged length of stay, vasopressor use, mechanical ventilation, and intensive care unit admission. Results We included a total of 94,114 primary COVID-19 hospitalizations for the analysis. Among them, 1575 (1.7%) had DVT. After adjusting for covariates, regression analysis showed that those with DVT had significantly greater odds for mortality (adjusted odds ratio [aOR], 2.34; 95% confidence interval [CI], 2.07–2.65), prolonged length of stay (aOR, 3.51; 95% CI, 3.16–3.91), vasopressor use (aOR, 4.23; 95% CI, 3.78–4.74), mechanical ventilation (aOR, 2.90; 95% CI, 2.38–3.53), and intensive care unit admission (aOR, 4.32; 95% CI, 3.85–4.84). Conclusions In our cohort, though only a few COVID-19 hospitalizations had DVT, the risk for adverse outcome was significantly higher. Therefore, healthcare providers should promptly monitor for DVT among COVID-19 patients and manage it promptly.