Postoperative adhesion often causes serious adverse effects such as bowl obstruction, chronic abdominal pain, pelvic pain, and infertility. We previously reported that a poly-L-lactic acid (PLLA) nanosheet can efficiently seal a surgical incision without scarring. In this report, we examined whether the PLLA nanosheet can form an effective anti-adhesion barrier in partial hepatectomy accompanied by severe hemorrhaging in rats. To evaluate the anti-adhesive property of the nanosheet, the liver wound surface was covered with TachoComb®, a well-known hemostat material used in clinical procedures, and then with the PLLA nanosheet. Dressing the wound surface with TachoComb® alone caused severe adhesion with omentum and/or residual parts of the liver. By contrast, combinational usage of TachoComb® and the PLLA nanosheet significantly reduced such adhesion, presumably by inhibiting the permeation of oozing blood cells and the infiltration of fibroblastic cells. Moreover, the nanosheet displayed low permeability against serum proteins as well as cells in vitro, supporting the notion that the PLLA nanosheet has anti-adhesive properties in vivo. These results strongly suggested that the PLLA nanosheet is a promising material for reducing unwanted postoperative adhesion. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 101B: 1251–1258, 2013.