Older age and cardiovascular comorbidities are well-known risk factors for all-cause mortality in COVID-19 patients. Hypertension (HT) and age are the two principal determinants of arterial stiffness (AS). This study aimed to estimate AS in COVID-19 patients requiring hospitalization and analyze its association with all-cause in-hospital mortality. This observational, retrospective, multicenter cohort-study analyzed 12,170 patients admitted to 150 Spanish centers included in the SEMI-COVID-19 Network. We compared AS, defined as pulse pressure {greater than or equal to} 60 mmHg, and clinical characteristics between survivors and nonsurvivors. Mean age was 67.5 {plus minus} 16.1 years and 42.5% were women. Overall, 2,606 (21.4%) subjects died. Admission systolic blood pressure (SBP) < 120 and {greater than or equal to} 140 mmHg was a predictor of higher all-cause mortality (23.5% and 22.8%, respectively, p < .001), compared to BP =120-140 mmHg (18.6%). The 4,379 patients with AS (36.0%) were older and had higher systolic and lower diastolic BP. Multivariate analysis showed that AS and SBP < 120 mmHg significantly and independently predicted all-cause in-hospital mortality (ORadj: 1.27, p=.0001; ORadj: 1.48, p=.0001, respectively) after adjusting for sex (males, ORadj: 1.6, p=.0001), age tertiles (second and third tertiles, ORadj: 2.0 and 4.7, p=.0001), Charlson Comorbidity Index (second and third tertiles, ORadj: 4.8 and 8.6, p=.0001), heart failure, and previous and in-hospital antihypertensive treatment. Our data show that AS and admission SBP < 120 mmHg had independent prognostic value for all-cause mortality in COVID-19 patients requiring hospitalization.