A system and method for providing dynamic quality-of-service (QoS) for Push-to-Talk (PTT) services in a wireless communications network. One or more servers interface to the wireless communications network to perform the PTT services for mobile units therein. Both the servers and the mobile units communicate with each other using control messages transmitted across bearers in the wireless communications network, and at least one of the servers transmits media streams comprised of voice messages for the PTT services between the mobile units across the bearers in the wireless communications network. At least one of the servers sets up a dedicated bearer in the wireless communications network for at least one of the mobile units, wherein the dedicated bearer has a specified quality of service (QoS) for transmission of at least the media streams to the mobile unit. The dedicated bearer may be static or dynamic.