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.

Relating Structure and Power: Comonadic Semantics for Computational Resources.- Coalgebraic Logics and Duality.- Intuitionistic Podelski-Rybalchenko Theorem and Equivalence between Inductive Definitions and Cyclic Proofs.- Undecidability of Equality for Codata Types.- Predicate Liftings and Functor Presentations in Coalgebraic Expression Languages.- Long-Term Values in Markov Decision Processes, (Co)Algebraically.- (In)finite Trace Equivalence of Probabilistic Transition Systems.- Steps and Traces.- On Algebras with Effectful Iteration.- Monoidal computer III: A coalgebraic view of computability and complexity.- Fibrational Bisimulations and Quantitative Reasoning.- Categorical Büchi and Parity Conditions via Alternating Fixed Points of Functors.