The vehicle system includes an output device, a plurality of rear seats, a plurality of belt buckle sensors provided on each of the plurality of rear seats, a plurality of seat belt reminder (SBR) sensors provided on each of the plurality of rear seats, and a controller. The controller is configured to determine one rear seat on which a passenger or an object having a weight equal to or less than a predetermined weight is located based on an output value of the SBR sensor, determine whether a seat belt corresponding to the determined rear seat is worn based on an output value of the belt buckle sensor, and control the output device to output a warning message when the vehicle is turned off and a door of the rear seat is not opened or closed in a state in which the seat belt is worn.