Abstract: PURPOSE: The current study examined whether multi-level ecological factors, including sociodemographic characteristics, military-related characteristics, social support, and community-level social vulnerability, were associated with loneliness among older U.S. Veterans. METHOD: We conducted a cross-sectional analysis of baseline data from a large clinical trial involving 237 Veterans aged ≥65 years hospitalized at a Midwestern Veterans Health Administration medical center. Loneliness was measured using the Three-Item Loneliness Scale. Multiple logistic regression models were used to assess associations between loneliness and multi-level ecological factors. RESULTS: Greater emotional/informational social support was significantly associated with lower odds of loneliness. Veterans residing in areas with moderate or high social vulnerability had higher odds of loneliness. No sociodemographic or military characteristics were significantly associated with loneliness after adjusting for all other factors. CONCLUSION: Findings highlight the importance of addressing individual and community-level social factors to reduce loneliness in older Veterans, supporting whole health approaches within gerontological care settings.