The Detroit-based union, with 1.3 million active and retired members mostly in key electoral states in the Midwest, said its executive board voted unanimously to endorse Gore.
"During the course of this campaign we have taken a long, hard look at the presidential candidates' positions and their programs for America's future," Yokich said in a statement.
"While two candidates have offered progressive, pro-working family programs, it is clear that only one of the progressive candidates can win this electionand that's Al Gore," Yokich said. "The UAW will go all-out to help Al Gore win this election."
The UAW, a powerful industrial union, has endorsed the Democratic candidate over the Republican candidate for decades.
For the first time this year, the UAW's 700,000 members who work for U.S. automakers will get Election Day off.
The announcement came on the same day Gore named Connecticut Sen. Joseph Lieberman, a strong advocate of pro-labor issues, his vice presidential candidate.
Yokich said Gore was on the UAW's side on the economy, workers' rights, education, the Social Security retirement program, Medicare, the environment and other issues of concern to working families.
He also expressed hope that Gore, as president, would seek to outlaw the use of permanent striker replacements.
"Al Gore believes that unions play an essential role in the economic and political life of America," Yokich said. "Unlike (Republican nominee) George W. Bush, Al Gore understands that our economy works best when working men and women have a real say in the workplace."
He added, "In contrast, George W. Bush offers nothing more or less than a replay of the voodoo economics of the 1980sa trillion-dollar-plus tax cut that would make the rich richer at the expense of working families."
Yokich expressed disappointment with Gore's record on trade issues, including the vice president's support for a measure to provide China with permanent normal trade relations with the United States, as well as the North American Free Trade Agreement (NAFTA) with Canada and Mexico.
"It's no secret that we disagreeand disagree sharply(with Gore) on NAFTA and on granting China permanent normal trade relations," Yokich said. "Yet even on trade where we don't see eye to eye, Al Gore is bettermuch betterthan George W. Bush."
Gore spokesman Doug Hattaway welcomed the endorsement, and said the vice president was committed to helping working families share in the nation's economic prosperity.
"Al Gore is honored and excited to be endorsed by one of America's great unions. They considered the candidates and saw that Al Gore is fighting for working families and will work to ensure that working families benefit from our prosperity, not just the privileged few," said Hattaway.
Bush campaign officials said the announcement was not a surprise, but said the Texas governor was still trying to win the votes of union members.
The UAW nod was not the first time this campaign season that a progressive-minded union has gone with Gore rather than Nader, who is generally considered to be more liberal.
In May, Americans for Democratic Action, a stalwart liberal group, endorsed the vice president despite a 66 percent lifetime voting rating from the group.