Patients with gastroesophageal reflux disease (GERD) present with heterogeneous symptoms, response to treatment, and physiologic profiles, requiring distinct and personalized management. This article provides a stepwise framework to phenotype GERD beginning with (1) characterization of symptom profile and response to acid suppression; (2) endoscopic evaluation of mucosal and anatomic integrity; (3) ambulatory reflux monitoring to characterize reflux burden and sensitivity; and (4) esophageal physiologic testing to assess gastroesophageal reflux mechanism and effectors of reflux clearance, and evaluate for alternate causes.