This paper designs a density-aware routing scheme for message delivery services in delay-tolerant networks that are characterized by tight constrains on intermittent connectivity, available storage and internode throughput in mobile ad hoc networks. This scheme includes inter-meeting time measure, node density estimation in proximity, boundary area detection, and message forwarding mechanisms. Mobile nodes can sense node density in their vicinities, and decide how to exchange messages with any encountered nodes during their movements. This scheme is scalable regardless of node population and need no extra localization facility. Simulation results show that the proposed scheme is simple and of less complexity, achieving comparable effects in terms of message delivery ratio and communication costs under nonuniform node distributions in delay-tolerant networks.