Background: Oncologists often struggle with managing the complex issues unique to older adults with cancer, and research is needed to identify patients at risk for poor outcomes. Methods: This study enrolled patients aged ≥70 years within 8 weeks of a diagnosis of incurable gastrointestinal cancer. Patient-reported surveys were used to assess vulnerability (Vulnerable Elders Survey [scores ≥3 indicate a positive screen for vulnerability]), quality of life (QoL; EORTC Quality of Life of Cancer Patients questionnaire [higher scores indicate better QoL]), and symptoms (Edmonton Symptom Assessment System [ESAS; higher scores indicate greater symptom burden] and Geriatric Depression Scale [higher scores indicate greater depression symptoms]). Unplanned hospital visits within 90 days of enrollment and overall survival were evaluated. We used regression models to examine associations among vulnerability, QoL, symptom burden, hospitalizations, and overall survival. Results: Of 132 patients approached, 102 (77.3%) were enrolled (mean [M] ± SD age, 77.25 ± 5.75 years). Nearly half (45.1%) screened positive for vulnerability, and these patients were older (M, 79.45 vs 75.44 years; P=.001) and had more comorbid conditions (M, 2.13 vs 1.34; P=.017) compared with nonvulnerable patients. Vulnerable patients reported worse QoL across all domains (global QoL: M, 53.26 vs 66.82; P=.041; physical QoL: M, 58.95 vs 88.24; P<.001; role QoL: M, 53.99 vs 82.12; P=.001; emotional QoL: M, 73.19 vs 85.76; P=.007; cognitive QoL: M, 79.35 vs 92.73; P=.011; social QoL: M, 59.42 vs 82.42; P<.001), higher symptom burden (ESAS total: M, 31.05 vs 15.00; P<.001), and worse depression score (M, 4.74 vs 2.25; P<.001). Vulnerable patients had a higher risk of unplanned hospitalizations (hazard ratio, 2.38; 95% CI, 1.08–5.27; P=.032) and worse overall survival (hazard ratio, 2.26; 95% CI, 1.14–4.48; P=.020). Conclusions: Older adults with cancer who screen positive as vulnerable experience a higher symptom burden, greater healthcare use, and worse survival. Screening tools to identify vulnerable patients should be integrated into practice to guide clinical care.