Background: Anemia following bariatric surgery is a known complication. To prevent nutrient deficiencies, adolescents require multivitamin/mineral supplementation following bariatric surgery. The purpose of this study was to investigate if routine multivitamin/mineral supplementation is sufficient to prevent anemia in adolescents undergoing bariatric surgery, particularly sleeve gastrectomy (SG), a procedure that may induce nutrient malabsorption. Methods: We conducted a retrospective review of pediatric patients who underwent SG (34 patients) and laparoscopic adjustable gastric banding (LAGB) (141 patients) (January 2006 through December 2013). We examined anemia marker levels (iron, ferritin, folate, B12, hemoglobin, and hematocrit) at first visit and 3, 6, and 12 months postsurgery by repeated-measures analysis adjusting for weight loss. Results: Following SG, folate levels decreased 3 and 6 months postsurgery but returned to baseline levels at 12 months. Furthermore, the SG group demonstrated lower folate levels compared with LAGB at 3 and 6 months. B12 levels decreased 6 months post-SG but returned to baseline at 12 months. Following LAGB, B12 levels decreased 12 months postsurgery compared with baseline. Ferritin levels decreased 3 months post-LAGB but returned to baseline levels at 6 months. There were no changes within groups or differences between groups in iron, hemoglobin, or hematocrit. Conclusions: While anemia did not occur in any patients while on recommended routine supplementation, folate levels were significantly reduced following SG and were lower in SG compared with LAGB patients. Additional folate supplementation seemed to improve folate levels, which highlights the importance of ongoing surveillance by primary care providers and the need for additional folate supplementation following SG.