This book constitutes the refereed proceedings of the 28th International Symposium on Practical Aspects of Declarative Languages, PADL 2026, held in Rennes, France, during January 2026.The 11 full papers and one short paper included in this book were carefully reviewed and selected from 24 submissions. The accepted papers span a range of topics related to functional and logic programming, including some novel applications of Answer Set Programming, language extensions, runtime monitoring, program transformations, type-checking, and applications of declarative programming techniques to artificial intelligence and machine learning, among others.