The 9th International Conference on Integration of Artificial Intelligence and Operations Research Techniques in Constraint Programming was held in Nantes, France, May 28-June 1, 2012. The aim of the CPAIOR conference series is to bring together interested researchers from constraint programming (CP), artificial intelligence (AI), and operations research (OR) to present new techniques or new applications in com- binatorial optimization and to provide an opportunity for researchers in one area to learn about techniques in the others. A main objective of this conference se- ries is also to give these researchers the occasion to show how the integration of techniques from different fields can lead to interesting results on large and complex problems. Therefore papers that actively combine, integrate, or contrast approaches from more than one of the areas were especially solicited. High-quality papers from a single area were also welcome. Finally, application papers showcasing CP/AI/OR techniques on innovative and challenging applications or experience reports on such applications were strongly encouraged. Submissions for this year were 64 papers. Each paper received at least three independent peer reviews which formed the basis for the acceptance of 26 papers. These papers are published in full in these proceedings. The Program Committee made a good job of providing thorough reviews and discussions.