The Vermont candidate kicked off his presidential campaign outside of the Capitol on Thursday.
"After a year of travel, discussion and dialogue, I have decided to be a candidate for the Democratic nomination for president," Sanders told his supporters in a statement. He is the first challenger facing Clinton in the Democratic primary.
Goals for combating income inequality, addressing climate change and reducing the influence of money in politics were laid out in his candidacy statement.
"I think it is time for the American people to say enough is enough," he said in an interview with The New York Times. "We need an economy that works for all of us and not just for a handful of billionaires."
Although officially an Independent and a self-identified socialist, Sanders will vie for the Democratic nomination -- a strategy with far greater odds of winning the presidency as opposed to running on the ballot as an independent, according to analysts.
Sanders is expected to launch his campaign with a rally in Vermont in a few weeks, Vermont Public Radio reported Wednesday.
One of his main platforms will be the welfare of the middle class in the United States, which Sanders believes has suffered in recent decades while the wealthy's bottom lines have grown exponentially.
Last week, Sanders voiced opposition to the White House's proposal for the largest international trade pact in history -- the Trans Pacific Partnership -- which is backed by 12 nations.
Congress had hoped to fast-track the trade deal but Sanders employed a little-used parliamentary tactic to delay work on the agreement because, he said, the American people deserve to know what the results of the pact will be.
"They told us NAFTA was going to create hundreds of thousands of new jobs. NAFTA cost us jobs," Sanders said, likening the deal to the controversial 1994 NAFTA trade agreement under President Bill Clinton.
"Instead of rubber-stamping the agreement, Congress and the public deserve a fair chance to learn what's in the proposal," he also said.
Sanders hinted last year that he was mulling a run for president.