Bariatric surgery (BaS) has steadily progressed through various procedures across the years to provide sustained rapid weight loss and resolution of obesity-related comorbidities. Current bariatric practice focuses on sleeve gastrectomy (SG) and roux-en-Y gastric bypass (RYGB). Sleeve gastrectomy has held steady as the most popular bariatric procedure, without entirely displacing the role of RYGB. In and of itself, SG is considered technically straightforward. Nevertheless, its performance is not free of complications, which can significantly impact patients’ quality of life. Presently, there is no societal consensus on definitive criteria to determine reoperation (e.g., conversion) as the sole therapeutic management for a failed primary SG. As SG continues to have a principal role in rapid weight loss surgery, a subset of patients will require conversion procedures. Contemporary practice directs RYGB as the most adequate re-operational surgery when considering conversion of primary SG due to gastroesophageal reflux disease (GERD), insufficient weight loss (IWL), and weight regain (WR). This chapter focuses on the evaluation, indications, approach, and outcomes of the conversion of SG to RYGB.