An image forming system to control an image forming apparatus by using a messenger application, a mobile device, and a method are provided. The image forming system includes a mobile device to activate a chat user interface to interface with an account of the image forming apparatus on the messenger application, and sending user messages to control a printing function of the image forming apparatus, a cloud server to receive the user messages from a messenger server, providing response messages of the account of the image forming apparatus in response to the user messages, and communicating with the mobile device in a conversational manner, thus controlling the printing of the image forming apparatus, and an image forming apparatus whose printing is controlled by the cloud server based on the user messages or providing monitoring information of a current status.