This book constitutes the proceedings of the 4th InternationalConference on Algorithms for Computational Biology, AlCoB 2017, held in Aveiro, Portugal, in June 2017. The 10 full papers presented together with 2 invited papers were carefully reviewed and selected from 24 submissions. They are organized in the following topical sections: Graph Algorithms for Computational Biology; Phylogenetics; and Sequence Analysis and Other Biological Processes.