Embodiments of the present invention provide an approach for a publisher-assisted, broker-based cache that can be utilized to reduce a volume of data (e.g., network traffic) delivered between a publisher and broker in a publication/subscription (pub/sub) environment. Specifically, in a typical embodiment, when a message is being generated on a publisher system, the publisher system will determine if the message includes a set of data that has a potential to be repeated in subsequent messages. Once such a set of data has been identified, the set of data will be associated/marked/tagged (e.g., in the message) with a unique identifier/cache key corresponding thereto (i.e., to yield a modified message). The modified message will be sent to a broker system, which will detect/locate the unique identifier, cache the corresponding data, and send the message along to any applicable subscriber systems. When a subsequent message that is supposed to contain the cached set of data is generated, the publisher system will instead substitute the unique identifier for the set of data to yield an abbreviated message and send the abbreviated message to the broker system. Upon receipt, the broker system will detect/locate the unique identifier, retrieve the corresponding set of data from the cache, replace the unique identifier with the set of data to yield a completed message, and then send the completed message to the applicable subscriber systems.