A method of providing a voice assistant service includes receiving a first voice command from a user. The method includes determining, from among a plurality of candidate devices, a plurality of devices that the first voice command is to be transmitted. The method includes transmitting information related to the first voice command to the plurality of devices. The method includes receiving, from the plurality of devices, a plurality of service provision messages generated in response to the first voice command and a plurality of pieces of service provision history information of the plurality of devices. The method includes selecting, based on the pieces of service provision history information, at least one of the plurality of service provision messages. The method includes outputting, based on the selected at least one service provision message, a response message in response to the first voice command.