This book constitutes the thoroughly refereed proceedings of the 12th International Conference on Collaborative Computing: Networking, Applications, and Worksharing, CollaborateCom 2016, held in Beijing, China, in November 2016. The 66 papers presented were carefully reviewed and selected from 116 submissions and focus on topics such as: Participatory sensing, crowdsourcing, and citizen science; Architectures, protocols, and enabling technologies for collaborative computing networks and systems; Autonomic computing and quality of services in collaborative networks, systems, and applications; Collaboration in pervasive and cloud computing environments; Collaboration in data-intensive scientific discovery; Collaboration in social media; Big data and spatio-temporal data in collaborative environments/systems; Collaboration techniques in data-intensive computing and cloud computing.