Described herein is a system for fastening a telematic module to the structure of a motor vehicle, in particular to the roof of the motor vehicle, comprising: a telematic module having a closed outer casing and containing at least one first connector for receiving signals and at least one electronic component for processing said signals; and a block for supporting said module, which is to be fixed to said structure of the motor vehicle and is equipped with a second connector designed for connection to said first connector. The system provides for mutual connection of the telematic module to the supporting block that implements an easy and fast mode of connection.