This book constitutes the refereed proceedings of the 18th International Conference and Workshops on Algorithms and Computation, WALCOM 2024, held in Kanazawa, Japan, during March 18–20, 2024. The 28 full papers presented in this book, together with two extended abstracts of invited talks, were carefully reviewed and selected from 80 submissions. They cover diverse areas of algorithms and computation, that is, approximation algorithms, algorithmic graph theory and combinatorics, combinatorial algorithms, combinatorial optimization, computational biology, combinatorial reconfiguration, computational complexity, computational geometry, discrete geometry, data structures, experimental algorithm methodologies, graph algorithms, graph drawing, parallel and distributed algorithms, parameterized algorithms, parameterized complexity, network optimization, online algorithms, randomized algorithms, and string algorithms.