This book constitutes the proceedings of the 14th International Conference on Language and Automata Theory and Applications, LATA 2020, which was planned to be held in Milan, Italy, in March 2020. Due to the corona pandemic, the actual conference was postponed and will be held together with LATA 2021.The 26 full papers presented in this volume were carefully reviewed and selected from 59 submissions. They were organized in topical sections named: algebraic structures; automata; complexity; grammars; languages; trees and graphs; and words and codes. The book also contains 6 invited papers in full-paper length.