Causal broadcast is at the core of collaborative applications, distributed databases, conferencing, or social networks. Existing causal broadcast algorithms are either not scalable or cannot be implemented on mobile networks because they do not take into account the features of these networks: limited capacities of nodes (computation, storage, energy), unreliable communication channels, and the dynamics of connections due to node mobility, node failure, and join/leave of nodes. This work presents a causal broadcast algorithm for mobile networks. The algorithm is scalable: control information piggybacked on messages and maintained on nodes is of small size. Experiments conducted on OMNeT++, a realistic network simulator, confirms the effectiveness of our causal broadcast protocol, rendering causal broadcast affordable in mobile networks.