Background/Objectives: Gastroesophageal reflux disease (GERD) is associated with extraesophageal syndromes that require an objective assessment of abnormal acid exposure to establish the diagnosis. The COuGH RefluX score has been proposed as a diagnostic tool for GERD in patients with chronic laryngopharyngeal symptoms. The aim of the study was to evaluate the diagnostic performance of the COuGH RefluX score in the Mexican population. Methods: A cross-sectional study was conducted in patients with chronic laryngopharyngeal symptoms. Patients with cough, globus, sore throat, dysphonia, and/or throat clearing of ≥8 weeks duration, 24 h pH-impedance monitoring (pH-IM), and without objective evidence of GERD (defined as acid exposure time >6%) were included in the study. The COuGH RefluX score tool was applied and stratified as low probability with ≤2.5 points, intermediate probability with 3.0 to 4.5 points, and high probability with ≥5.0 points. The kappa test assessed the concordance between both tests; the area under the curve (AUR), sensitivity (S), specificity (E), positive predictive value (PPV), and negative predictive value (NPV) were calculated for each result. Results: 164 patients were included; the prevalence of GERD by pH-IM was 32% vs. 40.3% by COuGH RefluX score, the agreement was weak (κ = 0.34; p < 0.001), but the AUR was good (0.720 ± 0.17; p < 0.001). A score ≤ 2.5 had S = 49%, E = 88%, PPV = 89%, and NPV = 42% to rule out proven GERD, while a score ≥ 5 had S = 65%, E = 71%, PPV = 52%, and NPV = 82% for proven GERD. Conclusions: The COuGH RefluX score has low sensitivity but adequate specificity for GERD diagnosis in Mexican patients with chronic laryngopharyngeal symptoms.