It is often assumed that political parties in Africa have only weak formal structures and are instead dominated by informal, personalised networks. This paper seeks to challenge this view by presenting a much more nuanced picture of intra-party dynamics. Based on unique survey data from Ghana, it is shown how formal and informal party structures co-exist and interact at the national and constituency level. Because informal relationships are not directly observable and difficult to study, the paper employs a social network approach to map the personal interactions between the Members of the 6th Parliament of Ghana and their respective parties. It is found that the local party organisation plays a strong role in both of the major parties NDC (National Democratic Congress) and NPP (New Patriotic Party). There are, however, also differences between the parties. At the national level, the NDC is strongly centralised and dominated by its national executives. The NPP, in contrast, has an informal power center located in the Ashanti Region. Ethno-regional factions play only a minor role in both parties. By demonstrating that the relative importance of informal relations varies even between parties in the same country, the paper contributes to a better understanding of the variation in party organisation across Africa.