This book constitutes the proceedings of the 15th Asian Symposium on Programming Languages and Systems, APLAS 2017, held in Suzhou, China, in November 2017. The 24 papers presented in this volume were carefully reviewed and selected from 56 submissions. They were organized in topical sections named: security; heap and equivalence reasoning; concurrency and verification; domain-specific languages; semantics; and numerical reasoning. The volume also contains two invited talks in full-paper length. .