Laparoscopic sleeve gastrectomy (SG) is a widely performed bariatric procedure due to its efficacy in weight loss and metabolic improvement. However, a major limitation of SG is the increased risk of gastroesophageal reflux disease (GERD), which affects a significant proportion of patients postoperatively. While Roux-en-Y gastric bypass (RYGB) is often preferred for patients with GERD, its higher complexity and risk of long-term complications make it unsuitable for some patients. The Koala Sleeve is an innovative modification of SG incorporating a horizontal gastroplasty to enhance lower esophageal sphincter (LES) function, reducing the incidence and severity of GERD while preserving weight loss outcomes. This study describes the technical aspects, rationale, and initial clinical results of the Koala-Sleeve technique. The procedure begins with a standard SG, followed by the placement of three horizontal mattress sutures at the gastroesophageal junction, forming a physiological flap-valve mechanism without requiring fundoplication. The initial clinical series of 15 patients demonstrated promising outcomes, with an average excess weight loss of 79% at 6 months and an 87% resolution rate of GERD symptoms. Compared to standard SG, the Koala Sleeve effectively mitigates reflux risk while maintaining weight loss efficacy. Additionally, its simplicity and short learning curve make it a feasible option for bariatric surgeons familiar with SG. While preliminary results are encouraging, further research with larger, multicenter studies and long-term follow-up is necessary to validate its durability and effectiveness. If confirmed, the Koala Sleeve could represent a paradigm shift in bariatric surgery by offering a safe and effective alternative for patients at risk of GERD following SG.