The 20-year-old made the announcement during the homestate leg of his My Kind of Christmas US tour (you can watch it here).
He told the crowd: "I would like to make a special announcement. I've chosen to serve a full-time mission".
Reduced to tears, Archuleta explained, "it's not because someone told me I was supposed to do it and not because I no longer want to do music anymore. It's because it's the feeling that it's what I need to do next in my life".
He will have to adhere to the rules of the Church of Jesus Christ of Latter Day Saints during his mission, including wearing a uniform. He will be permitted just two phonecalls home a year, both to his mother.
He continued: "It's the feeling that's allowed me to have the opportunities I've had, the challenges I've overcome and the blessings, too. And I've learned to trust that feeling and answer when it calls."