This comprehensive Research Handbook presents emerging theory and empirical research on group decision making across various disciplines, including psychology, communication, organizational behavior, and information science. Leading scholars assess the challenges impacting this topic and highlight opportunities for improving intra-group processes, including through incorporating new technologies and organizational frameworks. Chapters examine developments in structural issues such as team composition; affective issues such as psychological safety, trust, morale, and emotion; cognitive issues such as those influencing effective use of member's knowledge; and the impact of modern technologies such as generative artificial intelligence. This Research Handbook presents an extensive overview of group decision making, providing practical strategies to improve workflow and integrate digital developments. The Research Handbook on Group Decision Making is a valuable resource for scholars and students of business and management, psychology, communication studies and sociology. It will also benefit business leaders and managers, HR professionals and government officials due to its insights into increasing efficiency and effectiveness.