Let it go or let it grow? – Personal network development and the mobilization of intra-organizational social capital

•Longitudinal study on three waves of personal network data in nine organizations.•Newcomers mobilized about 20 % of potential network resources at each wave.•Change in network composition predicts increase in social capital mobilization.•Socio-emotional integration increases where alters are replaced, rather than added.•Findings suggest differences between newcomers based on gender.