The development of a Shared Mental Model (SMM) between team members and effecti'e communication of the shared knowledge have been ftwnd to improve teamwork perfiwtnance. However, humans may differ in how they produce and perceive communication acts according to their personality traits and this will affect development of the SMM. Whether, this is true of heterogeneous teams involving human and intelligent virtual agents (WAs) is unknown. In this paper, we explore the impact of IVA's with two different combinations of personality traits, i.e. extraversion and agreeableness. on the development of a SMM with human teammates. Additionally, this study investigated the influence of the match in the two personality traits between IVAs and humans on the development of a SMM. The results showed that agreeable lVAs positively impacted on the development of taskwork and teamwork SMMs; whereas extraversion did not influence development of the SMM. Moreover, when the collaborating human and IVA had matching agreeableness personality traits there was a positive influence on the SMM between them and better performance outcomes.