A portable communication apparatus, which communicates with vehicle control apparatuses that respectively control vehicles to achieve authentication with respect the vehicle control apparatuses, includes an authentication information change section and a post-change communication section. The authentication information change section communicates with a first vehicle control apparatus, by using a first communication technique, to change authentication information that is used in the first vehicle control apparatus to authenticate the portable communication apparatus. Upon receipt of a notice indicative of having changed the authentication information from the first vehicle control apparatus, the post-change communication section communicates with a second vehicle control apparatus, by using a second communication technique.