This book constitutes the thoroughly refereed papers of the 18th International Conference on Implementation and Application of Automata, CIAA 2013, held in Halifax, NS, Canada, in July 2013. The 25 revised full papers presented together with 3 invited papers and 7 short papers were carefully selected from 43 submissions. The papers cover various topics such as complexity of automata; compressed automata; counter automata; dictionary matching; edit distance; homing sequences; implementation; minimization of automata; model checking; parsing of regular expressions; partial word automata; picture languages; pushdown automata; queue automata; reachability analysis for software verification; restarting automata; transducers; tree automata; weighted automata; XML streams.