Mobile Groupware Systems employ devices such as PDAs and cellular phones to explore the opportunities that mobile technologies grant for cooperative work. However, due to the physical constraints related to these devices, such systems must adapt the content of information to user's context. This adaptation usually takes into account user's location and device. As for the users of Groupware Systems, mobile users need to be aware of what is going on inside the group in order to better perform their own activities. This refers to the notion of awareness support, which stands for the knowledge a user has about the group itself and her/his colleagues' activities. In this paper, we propose a context-based awareness mechanism for mobile Groupware Systems. This mechanism takes into account both the user's physical and organizational context in order to filter the awareness information and to deliver relevant information to mobile users.