There is provided a system and method for compressing voice-over-IP headers. More specifically, in one embodiment, there is provided a method comprising receiving a voice-over-IP packet including at least one packet header that contains a set of one or more packet header field values, selecting a content identifier that corresponds to the one or more packet header field values of the received packet, replacing at least one of the packet-header field values in the received packet with the selected content identifier, thereby to create a compressed voice-over-IP packet, and transmitting the compressed voice-over-IP packet across a network connection.