Heuristic search and other forms of combinatorial search optimization are very active areas of research in artificial intelligence, robotics, planning and other areas of computer science. The International Symposium on Combinatorial Search (SoCS) is meant to bring researchers in such areas together to exchange ideas and crossfertilize the field. SoCS is a forum for researchers and submissions in all fields that use combinatorial search, including artificial intelligence, planning, robotics, constraint programming, meta-reasoning, operations research, navigation, and bioinformatics. We also welcome submissions presenting real-world applications of heuristic search.The SoCS 2017 proceedings includes rigorously peer-reviewed long papers and short papers, as well as some extended abstracts that report preliminary results and ongoing work.