Background: Hospital-acquired pneumonia (HAP) is an important cause of mortality and morbidity among hospital-acquired infections. Vitamin D (25[OH]D) plays a role as an anti-inflammatory, immunomodulatory, and antimicrobial agent in infections. There are limited studies on the long-term mortality prediction of 25(OH)D deficiency in HAP and the findings are controversial. In this study, our primary aim was to investigate the role of 25(OH)D level measured during hospital admission as an independent risk factor for one-year mortality in HAP patients requiring intensive care. Materials and Methods: The retrospective study included patients that were diagnosed with HAP and admitted to the intensive care unit (ICU) between 2014 and 2018. Relationship between pretreatment 25(OH)D level and one-year independent mortality was evaluated. Vitamin D deficiency was defined as a 25(OH)D level of 20 ng/ml. Results: The study included 57 patients comprising 36 (63.2%) men and 21 (36.8%) women with a mean age of 75 years. One-year independent mortality occurred in 21 (36.8%) patients. Mean length of ICU stay was 16 days. Mean 25(OH)D level was 9.53 ng/ml, which was 20 ng/ml in 10 (17.5%) patients. No significant relationship was found between 25(OH)D level and one-year independent mortality and the length of ICU stay (p=0.477 and p=0.941, respectively). Similarly, no significant relationship was found between 25(OH)D level and APACHE II, age, length of ICU stay, and one-year independent mortality (p=0.621, p=0.933, p=0.410, and p=0.933, respectively). Conclusion: We consider that multicenter, double-blind randomized controlled studies are needed to substantiate the definition of vitamin D deficiency and the optimal vitamin D level to be achieved with replacement therapy in order to evaluate the effect of the therapy on the course of the disease and long-term independent mortality in HAP patients followed up in ICU.