The 21-year-old singer was far removed from her twerk-filled wild act that made headlines.
She sent a 22-year-old homeless, longhaired man to read out a note when her name was called as the winner.
"My name is Jesse. I am accepting this award on behalf of the 1.6 million runaways and homeless youth in the United States who are starving and lost and scared for their lives. I know, because I am one of those people," the man said while Cyrus wept on her seat.
"I have survived in shelters all over this city. The music industry will make over USD 7 billion this year, and outside these doors are 54,000 human beings who have no place to call home. If you want to make a powerful change in the world right now, join us and go to Miley's Facebook page," Jesse said.
In a video later, Cyrus said Jessie's appearance as her stand-in was not a stunt.
"Now is just the beginning for me. We gotta start somewhere," she said.
Cyrus is not the first celebrity to use an award show to highlight a cause.
Marlon Brando, who had won an Oscar for his role in 'The Godfather', had sent Sacheen Littlefeather to refuse the award on his behalf and deliver a 15-page speech where the actor had decried the mistreatment of Native Americans by the television and film industry.