The use of social media technologies in organizations has introduced novel ways of collaboration, communication, and knowledge sharing. In this respect, the present study is concerned with examining the use of one type of social media, the wiki technology, by members of several professional communities of practice to collaborate and share knowledge with each other. As such, it seeks to identify and understand the factors that influence their use of the wiki at a large multinational organization. To this end we used an interpretive exploratory case study which included 12 in-depth interviews with senior employees and managers as primary sources of data. Additional data was obtained during two field visits at the organization through observation of the wiki, field notes, and organizational documents. The study concludes with rich insights into the dual impact of the openness of wiki collaboration as well as the manner and value of using the wiki for knowledge collaboration and sharing at the workplace.