This book constitutes the proceedings of the 18th Asian Symposium on Programming Languages and Systems, APLAS 2020, held in Fukuoka, Japan, in December 2020.*

The 19 papers presented in this volume were carefully reviewed and selected from 46 submissions. They were organized in topical sections named: Invited Papers, Types, Program Analysis, Semantics, Language Design and Implementation, Concurrency, Verification, and Logic and Automata.

* The conference was held virtually due to the COVID-19 pandemic.