Recent findings indicate that more pronounced community heterogeneity is associated with lower levels of social capital. These studies, however, concentrate on specific aspects in which people differ (such as income inequality or ethnic diversity). In the present paper, we introduce the number of parties in the local party system as a more encompassing measure of community heterogeneity. This builds on the argument that the number of relevant socio-economic cleavages in the population (i.e. heterogeneity) determines the level of party system fragmentation. Using data on 307 Flemish municipalities, we find that municipalities with a more heterogeneous population indeed have lower levels of social capital. Hence, our study endorses--and generalizes--previous results linking community heterogeneity to lower levels of social capital.