Brown, a three-term senator from the swing state of OH, said he would continue the fight to make his "dignity of work" platform a centerpiece of the Democratic agenda, but that his party would be best served by him remaining in the US Senate.
"I will keep calling out Donald Trump and his phony populism", Brown, 66, said in a statement.
"Being president isn't something I have dreamed of my whole life or even for years", Brown said.
Brown, who was re-elected to the Senate to a third six-year term last year, had recently visited several early primary/caucus states including Iowa, New Hampshire, Nevada and SC. When Brown won election to his third Senate term in 2018, he was the only Democrat to win statewide, in part by holding the support of tens of thousands of Trump voters. Brown was comfortably re-elected in the November midterm elections, earning almost 10 percentage points more than Hillary Clinton did two years prior.
Throughout the past couple of months, Sherrod Brown has campaigned in four early primary and caucus states.
In addition to Brown not being fully committed to the rigors of a campaign, the likely candidacy of former Vice President Joe Biden also played into Brown's thinking. We've seen candidates begin taking up the dignity of work fight, and we have seen voters across the country demanding it-because dignity of work is a value that unites all of us. In the past few days, former First Lady, Secretary of State and the 2012 Democratic nominee, Hillary Clinton, has said she wouldn't run this time around.
"We're doing a dignity of work listening tour", Brown told CNN about the tour.
Brown's political appeal would have been greatest among Democrats who believe the party's surest path to the White House is through the industrial Midwest, nominating a candidate who can win enough Trump voters in Michigan, Wisconsin and Pennsylvania to reclaim those states.
"I will keep fighting for all workers across the country". That feat impressed many Democrats looking to take back the industrial states Trump swept on his way to victory in 2016, and sparked talk about a Brown candidacy.