In resent years, poly(lactic acid) (PLA) foams have been studied to replace traditional polymer foams in packaging field. Unfortunately, the foaming rate of PLA is low due to its low viscosity and elasticity. To overcome these shortcomings, a biodegradable polyester, poly(butylene adipate-co-terephthalate) (PBAT) was blended with PLA to improve melt properties of PLA. Additionally, maleic anhydride (MAH) and 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexane (L101) were added to improve the compatibility of PLA with PBAT. The blends were extruded into foams using a twin-screw extruder. The properties of extrudates were characterized by FTIR, DSC, ARES Rheometer, and SEM. The results show that complex viscosity of PLA/ PBAT blend increases by nearly 100% compared with pure PLA. Meanwhile, cell structure of foamed PLA/ PBAT blend is much larger and the distribution of cells is more homogenous. The foaming rate of PLA/ PBAT blend foams is raised by nearly 50% than that of pure PLA foams. POLYM. ENG. SCI, 49:1004-1012, 2009. (C) 2009 Society of Plastics Engineers