This thesis explores how the company-closed microblogging service Yammer affects internalknowledge sharing in Capgemini, a large, multinational consultancy company. The corporatemicroblog is a character-limited blog technology where participants in principle can connectto and exchange information with colleagues from all around the world. At present time, thephenomenon that is corporate microblogging has received ample academic attention, but itdoes seem that the technology has a considerable positive impact on knowledge-sharingactivities. Companies using Yammer have reported that they experience increased benefits interms of innovation, efficiency, increased inter-unit collaboration and improved, virtualcommunity building. This thesis explored how these benefits came about by collecting datawith a pilot survey through conducting in-depth interviews with active Yammer users. Theresults suggest that Yammer facilitates the creation of new and more efficient communicationpatterns, giving its users easier access to fellow colleagues. As a result of this new channel itsusers solves solves problems faster and (sometimes better), get fast feedback on ideas, and areable to locate and using old projects as references, to sell in new projects. Yammer was alsoidentified as a tool that could be used as a substitute for the informal water-coolerconversations that was not available for people working from a customer location. Thecorporate microblog does however struggle with low uptake among the employees inCapgemini, and people using it do have conflicting perceptions as to whether the tool onlyshould be considered as a productivity utility, or of it could also be used for socializationpurposes.