This book constitutes the thoroughly refereed post-workshop proceedings of the 11th International Workshop on Information Hiding, IH 2009, held in Darmstadt, Germany, in June 2009. The 19 revised full papers presented were carefully reviewed and selected from 55 submissions. The papers are organized in topical sections on steganography, steganalysis, watermarking, fingerprinting, hiding in unusual content, novel applications and forensics.