Opportunistic compression of replicated data in a content addressable storage system

An apparatus in one embodiment comprises a first storage system having a plurality of storage devices. The first storage system is configured to participate in a replication process with a second storage system. The first storage system comprises a replication engine configured to request from a data module of the first storage system at least one data page to be replicated to the second storage system as part of the replication process. If the requested data page is already available in compressed form in the data module, the replication engine receives the requested data page in compressed form and transmits it to the second storage system along with at least a portion of a content-based signature of the requested data page. If the requested data page is not already available in compressed form in the data module, the replication engine receives the requested data page in uncompressed form and transmits it to the second storage system.