This retrospective observational study aimed to provide insights on the use of clinical nutrition (CN) (enteral and parenteral feeding) and outcomes in an Italian real-world setting. The data source comes from administrative databases of 10 Italian Local Health Units. Patients diagnosed with malignant neoplasms from 1 January 2010 to 31 December 2015 were included. Metastasis presence was ascertained by discharge diagnosis in the hospitalization database. CN was identified by specific codes from pharmaceutical and hospitalization databases. Two cohorts were created-one for metastatic patients (N = 53,042), and one for non-metastatic patients (N = 4379) receiving CN. Two survival analyses were set for the cohort of metastatic patients-one included patients receiving CN and the second included malnourished patients. Our findings show that (1) administration of CN is associated with positive survival outcomes in metastatic patients with gastrointestinal, respiratory, and genitourinary cancer; (2) CN in malnourished metastatic patients with gastrointestinal and genitourinary cancer was associated with significant improvement in survival; (3) early administration of CN was associated with improvement in survival in non-metastatic patients with gastrointestinal cancer (HR 95%CI: 0.5 (0.4-0.6), p-value < 0.05). This study highlights the need to improve the assessment of nutritional status in oncologic patients and suggests a potential survival benefit of CN treatment in metastatic disease.