This book constitutes the thoroughly refereed post-conference proceedings of the 29th International Symposium on Logic-Based Program Synthesis and Transformation, LOPSTR 2019, held in Porto, Portugal, in October 2019. The 15 revised full papers were carefully reviewed and selected from 32 submissions. In addition to the 15 papers, this volume includes 2 invited papers. The symposium cover all aspects of logic-based program development, stages of the software life cycle, and issues of both programming-in-the-small and programming-in-the-large. This year LOPSTR extends its traditional topics to include also logic-based program development based on integration of sub-symbolic and symbolic models, on machine learning techniques and on differential semantics. The papers are grouped into the following topics: static analysis, program synthesis, constraints and unification, debugging and verification, and program transformation.