This book offers the exchange of ideas between scientists and technicians from both the academic and industrial sector which is essential to facilitate the development of systems that can meet the ever-increasing demands of today's society. The 18th International Symposium on Distributed Computing and Artificial Intelligence 2021 (DCAI 2021) is a forum to present the applications of innovative techniques for studying and solving complex problems in artificial intelligence and computing areas. The present edition brings together past experience, current work, and promising future trends associated with distributed computing, artificial intelligence, and their application in order to provide efficient solutions to real problems.This year's technical program presents both high quality and diversity, with contributions in well-established and evolving areas of research. Specifically, 55 papers were submitted to main track and special sessions, by authors from 24 different countries, representing a truly "wide area network" of research activity. The DCAI'21 technical program has selected 21 papers, and, as in past editions, it will be special issues in ranked journals such as Electronics, Sensors, Systems, Robotics, Mathematical Biosciences and ADCAIJ. These special issues cover extended versions of the most highly regarded works. Moreover, DCAI'21 special sessions have been a very useful tool to complement the regular program with new or emerging topics of particular interest to the participating community.