We analyse voluntary coalition formation using a unique panel data for 1056 municipalities in the French region of Brittany between 1995 and 2002. We use a control function approach to develop a binary discrete choice model with spatial interactions. We find that a municipality’s decision to cooperate over the provision of local public goods depends on the decisions made by its neighbours. In particular, the probability of cooperating with neighbouring municipalities is higher if the latter already provide joint local public goods. This suggests that functional cooperation is likely to emerge due to a mimicking motivation and is poorly motivated by political alignment. The results are in line with the recent applied spatial economics literature but are derived for a discrete choice model setting.