Background: Cervical anastomotic leaks (CALs) are significant complications following esophagectomy for esophageal cancer, leading to morbidity and prolonged hospital stays. Accurate and timely detection is critical to mitigate adverse outcomes. Objective: This study aims to compare the diagnostic accuracy, sensitivity, and specificity of oral water-soluble contrast (OWSC) and methylene blue (MB) in detecting CALs post-esophagectomy. Materials and methods: A single-center retrospective study was conducted on 692 patients with esophageal cancer who underwent transhiatal esophagectomy (THE) over 15 years. Patients underwent MB dye testing on the 7th postoperative day, followed by a Conray esophagogram on the 8th day. Leak classifications and outcomes were analyzed, and diagnostic accuracy, sensitivity, and specificity of both modalities were calculated. Results: Of the 692 patients, 110 (16%) developed CALs, with early leaks in 33% and late leaks in 67%. Methylene blue demonstrated higher diagnostic accuracy (96.8%) and sensitivity (87.3%) compared to OWSC, which had an accuracy of 88.8% and sensitivity of 80%. Both methods exhibited 100% specificity. The superior performance of MB over Conray swallow is not only clinically meaningful but also statistically significant (p = 0.0047). Conclusion: Methylene blue dye testing is a reliable, cost-effective, and statistically better bedside diagnostic tool for detecting CALs, especially in resource-limited settings. If the MB test is negative and there is a high clinical suspicion of leak, only then should further investigations, like a Conray esophagogram, be done.