Background Internal hernias (IHs) can occur after laparoscopic Roux-en-Y gastric bypass (LRYGBP), perhaps because of a lack of adhesion formation at the cut edges of the mesentery and a cutting through of sutures with a decrease in fat from weight loss. In patients undergoing reoperation after LRYGBP, we observed that bioabsorbable glycolide copolymer staple-line reinforcement (SLR) placed to mitigate staple-line bleeding had evoked adhesiogenesis and tissue fusion at the mesentery edges; therefore, we investigated whether use of this material decreases post-LRYGBP IH rates. Methods The records of the 43 patients (3%) in whom an IH developed during a mean follow-up time of 2 years in a series of 1,704 LRYGBP procedures were reviewed retrospectively. Results The IHs were in the Peterson's space (n = 4), the enteroenterostomy (n = 17), or the transverse mesocolon (n = 22). The IH rate was significantly higher in patients who had suture closure of the mesenteric defects at LRYGBP than in those without formal closure of the defects but in whom SLR was applied to the edges of the cut mesentery (P = 0.01). The suture-closure and SLR groups had similar demographic, operative, and follow-up characteristics. When transverse mesocolic IHs were excluded from analysis, patients given SLR remained less likely to have an IH (P = 0.05). Conclusion Use of bioabsorbable polymer SLR may decrease the occurrence of IHs after LRYGBP. Additional studies of the effect of mesentery closure method on IH incidence after LRYGBP are warranted.