About 50% of people diagnosed with autism have difficulties in developing any kind of functional language. This paper presents the development and evaluation of a multi-user collaborative game called ComFiM, for mobile tangible interfaces. The game was designed based on requirements of a group of children with autism, in order to stimulate communication through collaborative strategies. ComFiM was designed for interaction by pairs of users. Each user has a mobile tangible interface to share game resources and a TV as a shared space. ComFiM was evaluated following research aspects related to the interest of the users on the technology, the perception of each user's interlocutor and communication intentions observed between the users to collaborate with each other. Tests were carried out for 6 weeks with 4 children with autism. The results indicate that both the collaborative environment provided by the technology used as well as the strategies of the game have stimulated the users communication through this shared space.