A system and method of transmitting data by using a widget window are provided. A method of transmitting, by a first device, a file by using a widget window includes selecting a file stored in the first device, and moving the file to the widget window, when the file is moved to the widget window, displaying a device selection list, and, when at least one device is selected from the device selection list, providing the file to the selected device, wherein the file is provided to the selected device via a second device that is connected with the first device.