An alert system for rails that includes a cover assembly, sensors and an alert assembly is disclosed. There is a need to momentarily leave a child unattended while they sleep, for example. The child may unexpectedly awaken and attempt to climb over the rails of their crib. This is a dangerous situation that is to be prevented. Hence, the alert system includes a cover assembly that may be mounted and secured on top of railings of all sorts, such as a bed, crib or gate. The sensors may be configured to detect weight thereon and upon detection of a predetermined weight threshold being surpassed may generate alerts through the alert assembly. The alerts occur in the form of lights, an audible alarm through speakers, or to a mobile device. Thereby allowing alerts to occur even when the guardian and child are not near one another.