This book constitutes the refereed post-conference proceedings of the 9th International Conference on Nature of Computation and Communication, ICTCC 2023, held in Ho Chi Minh City, Vietnam, in October 2023. The 12 revised full papers presented were carefully selected from 30 submissions. The papers of ICTCC 2023 cover formal methods for self-adaptive systems and discuss natural approaches and techniques for natural computing systems and their applications.