These proceedings contain the papers presented at ANTS 2014, the 9th International Conference on Swarm Intelligence, held at IRIDIA, Université Libre de Bruxelles, Brussels, Belgium, during September 10–12, 2014. The ANTS series started in 1998 with the First International Workshop on Ant Colony Optimization (ANTS 1998), which attracted more than 50 participants. Since then ANTS, which is held bi-annually, has gradually become an international forum for researchers in the wider field of swarm intelligence. In 2004, this development was acknowledged by the inclusion of the term “swarm intelligence” (next to “ant colony optimization”) in the conference title. Since 2010, the ANTS conference is officially devoted to the field of swarm intelligence as a whole, without any bias toward specific research directions. This is reflected in the title of the conference: “International Conference on Swarm Intelligence.” The papers contained in this volume were selected out of 55 submissions. Of these, 17 were accepted as full-length papers, while nine were accepted as short papers. This corresponds to an overall acceptance rate of 47%. Also included in this volume are seven extended abstracts. All the contributions were presented as posters. The full-length papers were also presented orally in a plenary session. Extended versions of the best papers presented at the conference will be published in a special issue of the Swarm Intelligence journal.