Background: Gastric cancer (GC) remains a leading cause of cancer-related mortality worldwide, with a disproportionate burden in low- and middle-income countries. Guatemala reports among the highest mortality rates in Central America, yet institutional data remain limited.

Methods: This retrospective cohort study included 307 patients with histologically confirmed gastric adenocarcinoma treated at the Guatemalan Social Security Institute between 2014 and 2017. Demographic, clinicopathological and treatment variables were analysed. Overall survival (OS) was estimated using Kaplan–Meier methods and compared using the log-rank test. Cox proportional hazards models identified independent prognostic factors.

Results: The median age at diagnosis was 63 years; 86% of patients were aged >40 years, and 66.4% were male. At presentation, 53.7% had stage IV disease. The median OS was 8.4 months overall. Survival differed significantly by stage (p < 0.001), with median OS of 61.7 months (stage I), 43.9 (stage II), 14.2 (stage III) and 4.6 (stage IV). In multivariate analysis, underweight status (HR 1.55; 95% CI 1.08–2.22; p = 0.04), gastroesophageal tumour location (HR 1.48; 95% CI 1.02–2.16; p = 0.04), poorly differentiated histology (HR 2.05; 95% CI 1.42–2.88; p < 0.001) and advanced stage (stage IV HR 9.47; p < 0.001) were independently associated with mortality.

Conclusion: GC in Guatemala is predominantly diagnosed at advanced stages and associated with poor survival. Strengthening early detection, nutritional assessment and access to multimodal treatment is urgently needed in resource-limited settings.