A method for processing a voice input and a system therefor are provided. The system includes a microphone, a speaker, a processor, and a memory. The processor, in a first operation, receives a first voice input including a first wake-up keyword, selects a first response model based on the first voice input, receives a second voice input after the first voice input, processes the second voice input, using an NLU module, generates a first response based on the processed second voice input, in a second operation, receives a third voice input including a second wake-up keyword different from the first wake-up keyword, selects a second response model based on the third voice input, receives a fourth voice input after the third voice input, processes the fourth voice input, using the NLU module, and generates a second response based on the processed fourth voice input.