If autonomous agents interact with people, they should achieve the suspension of disbelief in order to offer a good interaction experience to users. To achieve this it is important that the agents' behaviours are consistent with a given personality since people have a tendency to attribute personality to interactive artifacts. The concept of personality is also useful to create diversity in multi-agent simulations even if users do not directly engage in the interactions, for example, to explore different strategies in simulated societies. This paper presents a computational model of personality based on the Five Factor Model of personality for the behaviour of social autonomous agents that interact in teamwork scenarios.