This book constitutes the thoroughly refereed post-conference proceedings of the 14th International Workshop on Coalgebraic Methods in Computer Science, CMCS 2018, colocated with ETAPS 2018, held in Thessaloniki, Greece, in April 2018.The 10 revised full papers were carefully reviewed and selected from 17 submissions. Also included are the extended abstracts of two keynotes/invited talks. The papers cover a wide range of topics in the theory, logics and applications of coalgebras.