Background <p>Vitamin D plays a key role in regulating the immune system and vaccine response, and hypovitaminosis D is a known risk factor for mortality. However, its potential influence on mortality in SARS-CoV-2 vaccinated older adults remains underexplored. This study aims to examine survival differences between unvaccinated and vaccinated older adults with varying vitamin D levels, and to assess the impact of vitamin D on mortality.</p> Methods <p>We recruited patients aged 65 and over from the Geriatrics Unit of Azienda Ospedale - Università Padova. Clinical, pharmacological data, including vaccination status and vitamin D levels, were collected at admission, alongside mortality data 12 months post-hospitalization. Participants were divided into three groups: unvaccinated, vaccinated with vitamin D levels of 25–50 nmol/L, and vaccinated with levels &gt; 50 nmol/L.</p> Results <p>A total of 126 participants were included (56% women, mean age 83 years). No significant differences were found in COVID-19 severity among the three groups. After 12 months, 24 deaths were recorded: 17% in unvaccinated, 19% in vaccinated with low vitamin D, and 20% in vaccinated with high vitamin D (<i>p</i> = 0.94). Kaplan-Meier curves showed that mortality risk for vaccinated individuals with low vitamin D was similar to unvaccinated patients but significantly higher than vaccinated individuals with high vitamin D (<i>p</i> = 0.04). Vitamin D levels of 25–50 nmol/L were associated with a threefold increased risk of 12-month mortality (HR: 3.79, <i>p</i> &lt; 0.001).</p> Conclusions <p>Vitamin D levels can impact mortality in older vaccinated individuals. Early correction of vitamin D deficiency could potentially enhance outcomes.</p>