Collective awareness becomes an important construct in the virtual context. It allows facing problems derived from uncertainty and ambiguity of electronic relationships and virtual environment. Considered as a dynamic concept, collective awareness develops with time and accumulated information exchanged between team members. However, virtual teams have different configurations resulting from different characteristics such as long/short lifespan, homogeneity/heterogeneity of team members, etc. This implies that processes of collective awareness building are different from one configuration to another. The purpose of this paper is to analyze how changing virtuality levels influence the dynamic of collective awareness. After theoretical analysis of both concept of virtuality and collective awareness, the paper present the steps and the results of a qualitative case study. This study compares two types of virtual teams (pure and hybrid) and explain differences found in collective awareness building mechanisms. Results of our study show that in team having short life span and whose members work together for the first time, it is difficult to build collective awareness. However teams having enough time to accomplish work, to exchange social and work related information, and to build personal relationships, can succeed to build a shared understanding of the actions of the others and visibility of their actions.