This book constitutes the proceedings of the 26th International Conference on Developments in Language Theory, DLT 2022, which was held in Tampa, FL, USA, during May, 2022. The conference took place in an hybrid format with both in-person and online participation. The 21 full papers included in these proceedings were carefully reviewed and selected from 32 submissions. The DLT conference series provides a forum for presenting current developments in formal languages and automata.