We develop a dynamic model to analyze the sources and the evolution of social participation and social capital in a growing economy characterized by exogenous technical progress. We start from the assumption that the well-being of agents basically depends on material and relational goods. Material goods can replace relational ones for the satisfaction of social needs, or, at least, for compensating the deprivation of human interactions. We point out the role of technical progress and the substitutability/complementarity between the two kinds of good in social interaction and the accumulation of social capital. We find that, in best case scenarios, technology may play a crucial role in supporting a “socially sustainable” economic growth.