Aim: To evaluate the clinical significance of positive malignant cells in peritoneal washings and their correlation with the stage of disease and clinico-pathological parameters in patients with gastrointestinal malignancies. Material and Methods: This prospective observational study included 80 patients with histologically confirmed gastrointestinal malignancies. Peritoneal washings were collected intraoperatively during surgical exploration or diagnostic laparoscopy and analyzed for malignant cells using standard cytological techniques. Data on patient demographics, primary tumor site, tumor grade, and clinical staging were recorded. Statistical analysis included Chi-square tests, ANOVA, and logistic regression to evaluate correlations between cytological findings and disease characteristics. Results: Positive cytology findings increased significantly with disease stage, from 16.67% in Stage I to 88.37% in Stage IV. Tumor grade also correlated strongly with cytological positivity, with 88.24% of high-grade tumors exhibiting malignant cells compared to 30.77% of low-grade tumors. The colon and rectum demonstrated the highest cytological positivity rates (80.00%), followed by gastric cancers (66.67%). Logistic regression analysis identified disease stage as the strongest predictor of positive cytology (OR = 3.45, p < 0.001), followed by male sex (OR = 2.15, p = 0.021) and older age (OR = 1.02, p = 0.005). Conclusion: Peritoneal cytology is a valuable prognostic tool in gastrointestinal malignancies, showing a strong association with advanced disease stages, high tumor grades, and specific primary tumor sites. Routine integration of peritoneal cytology into clinical practice can enhance staging accuracy, guide treatment strategies, and improve patient outcomes.