This book constitutes the thoroughly refereed post-conference proceedings of the 9th Interntaional Workshop on Digital Watermarking, IWDW 2010, held in Seoul, Korea, in October 2010. The 26 revised full papers presented were carefully reviewed and selected from 48 submissions. The papers are organized in topical sections on forensics, visual cryptography, robust watermarking, steganography, fingerprinting, and steganalysis.