This will be the 77-year-old senator's second bid for the White House after the unsuccessful one of 2016.
Addressing people on Vermont Public Radio, Sanders said: “I wanted to let the people of the state of Vermont know about this first.”
The self-described Democratic socialist joins an already crowded field of candidates seeking to take on President Donald Trump and the Republicans in 2020.
Sanders gave a summary of how he will campaign. He said: “And what I promise to do is, as I go around the country, is to take the values that all of us in Vermont are proud of - a belief in justice, in community, in grassroots politics, in town meetings - that's what I'm going to carry all over this country."
He called Trump a national embarrassment and a pathological liar and said he is a racist, a sexist, a homophobe and a xenophobe. He described Trump as somebody who is gaining cheap political points by trying to pick on minorities, often undocumented immigrants.