A thin film transistor array panel including a display area having a gate line, a data line insulated from and intersecting the gate line, a thin film transistor connected to the gate line and the data line, and a pixel electrode connected to the thin film transistor, and a peripheral area formed on the circumference of the display area, according to an exemplary embodiment of the present invention, includes: a driving signal line formed with the same layer as the gate line in the peripheral area and receiving an external signal; a connection signal line formed with the same layer as the data line in the peripheral area; a disconnection prevention member overlapping the side surface of the connection signal line on the connection signal line; and a connection assistance member formed on the disconnection prevention member and connecting the driving signal line and the connection signal line.