This study was designed to evaluate the effect of polyethylene glycol (PEG) and nonsteroidal anti-inflammatory drug (ibuprofen) on the prevention of postsurgical tissue adhesion. For this, poly(L-lactic acid) (PLLA)-PEG diblock copolymers were synthesized by ring opening polymerization of L-lactide and methoxy polyethylene glycol (Mw 5000) of different compositions. The synthesized copolymers were characterized by gel permeation chromatography and 1H-nuclear magnetic resonance spectroscopy. PLLA-PEG copolymer films were prepared by solvent casting. The prepared copolymer films were more flexible and hydrophilic than the control PLLA film, as investigated by the measurements of glass transition temperature, water absorption content, and water contact angle. The drug release behavior from the ibuprofen (10 wt%)-loaded copolymer films was examined by high performance liquid chromatography. It was observed that the drug was released gradually up to about 40% of total loading amount after 20 days, depending on PEG composition; more drug release from the films with higher PEG compositions. In vitro cell adhesions on the copolymer films with/without drug were compared by the culture of NIH/3T3 mouse embryo fibroblasts on the surfaces. For in vivo evaluation of tissue anti-adhesion potential, the copolymer films with/without drug were implanted between the cecum and peritoneal wall defects of rats and their tissue adhesion extents were compared. It was observed that the ibuprofen-containing PLLA-PEG films with high PEG composition (particularly PLLA113-PEG113 film with PEG composition, 50 mol%) were very effective in preventing cell or tissue adhesion on the film surfaces, probably owing to the synergistic effects of highly mobile, hydrophilic PEG and anti-inflammatory drug, ibuprofen.