This book constitutes the refereed proceedings of the 18th International Symposium on Theoretical Aspects of Software Engineering, TASE 2024, held in Guiyang, China, during July 29-August 1, 2024. The 24 full papers, 2 short papers, 1 invited abstract and 1 invited papers were carefully selected from 76 submissions. The papers presented new results on innovative advances in software engineering, as well as the latest developments in formal and theoretical software engineering methods and techniques.