The present invention provides an output circuit with electrostatic discharge (ESD) protection in a semiconductor chip of a source driver. The source driver is configured to drive a display panel. The output circuit includes an output buffer, an output pad, a switch and a first resistor. The switch is coupled between the output buffer and the output pad, wherein data voltages for driving the display panel are transmitted from the output buffer to the output pad via the switch. The switch includes a first metal oxide semiconductor (MOS) transistor, which includes a first terminal coupled to the output pad, a bulk terminal and a gate terminal. The first resistor is coupled between the bulk terminal of the first MOS transistor and a first power supply terminal.