In this paper, we study how interoperability between networks of mobile money agents impacts the choice of mobile network operators using survey data for Tanzania. Using the geo-location of respondents, we combine survey data with information on the proximity of mobile money agents. We estimate discrete choice models where consumers’ decision to subscribe to a mobile network operator (and mobile money provider) depends on the distance from their providers’ mobile money agent. Our results suggest that the distance to agent has a significant impact on the subscription decision. Imposing interoperability at the level of mobile money agents, with consumers using the closest agent from any mobile money provider, we find that interoperability at the level of agents has only a small impact on the market shares of mobile network operators. Smaller operators marginally gain because their consumers can now use agents of larger providers which tend to be closer. We conclude that interoperability on the level of agents does not have a large impact on market structure in the case of Tanzania in the period considered.