This book constitutes the thoroughly refereed post-conference proceedings of the 27th IFIP WG 1.3 International Workshop on Algebraic Development Techniques, WADT 2024, held in Enschede, The Netherlands, on July 8, 2024.The 6 full papers presented in this volume were carefully reviewed and selected from 11 submissions. The contributed presentations covered a wide range of topics on the algebraic approach to system specification: from foundations of algebraic-specification languages to institutions and knowledge representation, to graph transformations, rewrite rules, process algebra, and bialgebraic frameworks, to many-logics modal systems and quantum process calculi, and to several applications to code synthesis and maintainability.