Background: Parathyroid hormone (PTH) is closely linked to mineral metabolism, kidney function, inflammation, and cardiovascular disease. However, its clinical significance in unselected hospitalized populations remains insufficiently characterized. We aimed to evaluate the prevalence of elevated PTH and its association with long-term mortality in a real-world cohort of internal medicine inpatients. Methods: In this retrospective cohort study, electronic records of adults hospitalized in an internal medicine department in 2019 were reviewed. Patients with available in-hospital PTH measurements were included. Elevated PTH was defined as >88 pg/mL. Clinical characteristics and laboratory parameters were recorded. The primary outcome was all-cause mortality with a minimum follow-up of 2 years. Cox proportional hazards models adjusted for clinically relevant covariates were used to examine the association between PTH and mortality. Results: A total of 1595 patients were included, of whom 567 (35.5%) had elevated PTH levels. Patients with elevated PTH were older and had a higher burden of chronic kidney disease, cardiovascular disease, and inflammatory and nutritional abnormalities. During a mean follow-up of 22 ± 13 months, mortality occurred more frequently in patients with elevated PTH than in those with normal levels (56.1% vs. 33.7%, p < 0.001). After multivariable adjustment, elevated PTH remained independently associated with increased mortality risk-adjusted HR (1.36, 95% CI 1.15–1.62, p < 0.001). Conclusions: Elevated PTH is common among hospitalized internal medicine patients and is associated with increased long-term mortality. PTH may represent an integrated biomarker reflecting disease burden, inflammation, and renal dysfunction and could contribute to risk stratification in hospitalized populations. Prospective studies are warranted to clarify underlying mechanisms and clinical implications.