The use of prehabilitation has grown among individuals undergoing multimodal management for oesophagogastric cancer (OGC). Most available research has consisted of limited, single-centre studies. This multi-institutional project was designed to evaluate how prehabilitation influences outcomes after surgery for OGC. Information was pooled from four prospective studies conducted in the UK and Ireland involving patients treated with multimodality therapy for OGC. These included three randomised trials and one observational comparison, each examining a prehabilitation protocol versus standard care. The intervention combined aerobic exercise, supervised by physiologists, and nutritional counselling was maintained across the treatment timeline. The main outcome was survival (both overall and disease-related mortality). Secondary endpoints assessed postoperative complications, cardiorespiratory performance (VO₂ peak and anaerobic threshold (AT)), completion of chemotherapy, hospital stay duration, body mass index change, tumour regression, and rates of pneumonia or anastomotic leak. Adjusted hazard ratios (HR) and odds ratios (OR) with 95% confidence intervals (CI) were generated using Cox and logistic regression. Out of 165 total participants, 88 underwent prehabilitation while 77 served as controls. Prehabilitation did not significantly improve overall or disease-specific mortality (HR 0.67, 95% CI 0.21-2.12 and HR 0.82, 95% CI 0.42-1.57, respectively). Major postoperative complications were less common among prehabilitation participants (20% vs. 36%, p = 0.034; adjusted OR 0.54; 95% CI 0.26-1.13). Decline in VO₂ peak following neoadjuvant treatment was smaller in the prehabilitation arm (−1.07 mL/kg/min vs. −2.74 mL/kg/min; p = 0.035), and chemotherapy completion was higher (90% vs. 73%; p = 0.016). Hospitalisation length (10 vs. 12 days; p = 0.402) and tumour response (Mandard 1-3: 41% vs. 35%; p = 0.494) slightly favoured the prehabilitation group but lacked statistical significance. While methodological variation existed between studies, combined findings indicate several potential clinical advantages of prehabilitation before OGC surgery. Ongoing national standardisation projects and future trials are expected to further optimise these programmes and solidify their evidence base.