The two-volume set, LNCS 15434 and 15435, constitutes the refereed post-conference proceedings of the 17th International Conference on Combinatorial Optimization and Applications, COCOA 2024, held in Beijing, China, during December 6&8, 2024. The 53 full papers included in the proceedings were carefully reviewed and selected from 124 submissions. They deal with combinatorial optimization and its applications, including algorithm design, theoretical and experimental analysis, and applied research of general algorithmic interest.