Background: The presence of cardiophrenic lymph nodes (CPLN) was potentially associated with peritoneal involvement in patients with abdominal malignancies. In this study, gastric cancer patients were investigated for the relationship between CPLN and peritoneum metastases. Methodology: Peritoneal exploration was performed on 516 gastric cancer patients between 2017 and 2019, including 134 (26%) with peritoneal metastases (PM). An univariate and multivariate analysis of preoperative computed tomography (CT) scans was conducted to assess the association between CPLN and confirmed PM. Results: Among the factors associated with CPLN in the univariate analysis, PM accounted for the strongest association (P < 0.001). In the multivariate analysis, PM was the only independent factor associated with CPLN (odds ratio [OR], 7.8; 95% confidence interval [CI], 4.6 similar to 13.0; P < 0.001). CPLN was significantly more common in the 38 patients with classic signs of PM compared to the 96 patients without visible signs of PM (36/38 [95%] versus 76/96 [79%]). CT scan sensitivity rose from 28% (38/134 patients) to 85% (114/134 patients) with CPLN detection added to other diagnostic signs of PM. Conclusion: Detecting CPLN on CT was a valuable tool for diagnosing peritoneal metastases of gastric cancer.