According to one aspect, the subject matter described herein includes a method for Diameter-based steering of mobile device network access. The method includes receiving a Diameter message associated with a mobile device. The method also includes determining, based on the Diameter message, whether the mobile device should be steered to access a radio access network or a radio access network type that is different from a radio access network or radio access network type currently supporting network access of the mobile device. The method further includes, in response to determining that the mobile device should access the different radio access network or radio access network type, steering the mobile device to access the different radio access network or radio access network type.