A hydraulically operated ladder brace designed for transporting, for deploying and for supporting a standard, mobile extension ladder and intended to be pivotally attached to a rack system mounted on the rear portion of a vehicle. The ladder brace consists of a U-shaped frame comprising two elongated members and a cross piece operatively connected with a hydraulic ram and cylinder device. In its transport position, the ladder brace is positioned with the U-shaped frame lying substantially in a horizontal plane and pivotally attached to the rack system. The ladder brace is designed such that a standard extension ladder, such as an aluminum ladder having open ended hollow rungs, may be positioned in parallel relationship with and between both of the elongated members. The ladder brace is further designed to allow depolyment from the transport position through activation of a hydraulic pump which causes a ram to extend outwardly from a hydraulic cylinder thus causing the U-shaped frame to pivot the ladder from a horizontal position through an arc into a position of deployment.