Inappropriate long-term use of Proton Pump Inhibitors (PPIs) is a public health challenge. It is uncertain if this "implementation gap" is driven by knowledge deficits or other behavioural barriers. This study aimed to quantify systematic de-prescribing protocol (SDP) use and identify barriers to PPI de-prescribing among Internal Medicine (IM) and Gastroenterology (GI) physicians. A cross-sectional survey was conducted among 310 physicians (IM, GI) from three Indian states. A validated questionnaire assessed knowledge, self-efficacy, barriers, and use of an SDP (the primary outcome). A multivariable logistic regression model, robust for clustering, identified predictors of SDP use. Physician knowledge was high (mean 3.7/4.0), but a "knowledge–implementation gap" was evident: 85.2% agreed de-prescribing was "crucial," yet only 28.4% used an SDP. Gastroenterologists (40.0%) were twice as likely as IM physicians (20.0%; p=0.0002) to use an SDP. In the adjusted model, GI specialty (aOR 2.59) and higher self-efficacy (aOR 1.82) were the strongest predictors. The highest-rated barriers were 'Patient resistance/anxiety' (78.0%) and 'Consultation time constraints' (69.2%). In this cohort, PPI over-prescription appears driven by implementation failure and clinical inertia, not knowledge deficits. This is associated with low self-efficacy and barriers like patient anxiety and time pressure. The specialty disparity suggests confidence, not just knowledge, is key. Interventions must pivot from education to systemic solutions targeting these behavioural barriers.