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, prools, 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.