In this paper, we use the social capital theory to extend the topic about the evolution of industrial districts, aiming to verify whether or not social capital may be considered as a critical source in explaining the dynamics of population of co-localised organisations towards the phenomenon of passive internationalisation. The study explores these issues by analysing the pattern of fragmentation of production and the change of internal rules of actors inside a textile industrial district localised in the Center of Italy – Val Vibrata – after the “internal invasion” of foreign business players in different stages of chain value. We use these empirical data to calibrate a computer simulation model so to generate a number of near-histories that capture possible unfolding cluster dynamics.