This volume contains the research papers presented at the International C- ference on Automated Reasoning with Analytic Tableaux and Related Methods (TABLEAUX 2009) held July 6-10, 2009 in Oslo, Norway. This conference was the 18th in a series of international meetings since 1992 (listed on page IX). It was collocated with FTP 2009, the Workshop on First-Order Theorem Proving. The Program Committee of TABLEAUX 2009 received 44 submissions from 24 countries. Each paper was reviewed by at least three referees, after which the reviews were sent to the authors for comment in a rebuttal phase....