Background: Patients with lung cancer experience higher rates of hospitalization due to their elevated mortality and associated comorbidities. Hospital admissions among oncology patients often indicate organ vulnerability and are linked to poor prognosis. This study aimed to assess the characteristics and potential prognostic factors of hospitalized lung cancer patients. Methods: We retrospectively analyzed 646 patients admitted from June 2021 to May 2022 to the Medical Oncology Service at La Paz University Hospital (Madrid, Spain). Results: During this period, 158 patients admitted had lung cancer (24.5%). The median overall survival since admission (mOSSA) was 3.3 months (95%CI: 1.86–7.74). In the univariate analysis, poorer mOSSA was associated with admission for tumor-related causes (1.33 vs. 7.30 months, p p p = 0.044). In the multivariate analysis, independent prognostic factors included admission for tumor-related causes (p = 0.032, aHR 1.81, 95%CI: 1.05–3.11) and ECOG ≥ 2 (p = 0.041, aHR 1.80, 95%CI: 1.03–3.16). Conclusions: Hospital admission for lung cancer is a poor prognostic event, particularly when associated with tumor-related causes or a decline in performance status.