Caller ID information provided coincident to a Voice over IP (VoIP) call is validated by one or more network devices. An originating router detects an offered IP address associated with a calling party node, for example, upon receiving a SIP Invite message initiated by the calling party node. The originating router determines the validity of the offered IP address and hence determines the validity of the Caller ID information based on the validity of the offered IP address. The originating router sends indicia of the validity to a terminating router, connected to a called party node, by inserting a verification bit in the SIP Invite message and sending the transformed SIP Invite message to the terminating router. Alternatively, the terminating router may query the originating router for indicia of validity. Upon receiving the indicia of validity, the terminating router may notify the called party node and so inform the called party whether it can rely on the Caller ID information.