"In my view, God willing, it'll be Secretary Clinton," Biden said, referring to the next president, during an address at the American Constitution Society convention in Washington.
Biden made his endorsement as he talked about the battle in Washington to fill a Supreme Court vacancy created by the death of Justice Antonin Scalia, and "dysfunction" in Congress he said is "undermining the norms of how we conduct our government."
Biden also unleashed a series of blistering attacks against Clinton's opponent, presumptive Republican nominee Donald Trump, who he said was "literally undermining, and threatening and potentially doing damage to the constitutional imperative of an independent judiciary."
He called Trump's attacks on a Mexican-American judge presiding over lawsuits against Trump University "reprehensible," "racist" and "a dangerous attack on a vital pillar of democracy."
Trump last week said U.S. District Judge Gonzalo Curiel, who is presiding over lawsuits against Trump University, was biased against him because of his Mexican-American heritage.
Biden said such attacks by a candidate from a major political party make Trump unable to be "trusted to respect the independence of the judiciary as president."
"These are words of someone who sees our federal judiciary ... as a tool to manipulate to do what he calls 'to deal with the laws of our country,'" Biden said. "I don't think the framers envisioned a presidential candidate accusing a judge of being incapable of reaching a fair decision because of his ethnic decent.
"I find Donald Trump's conduct in this regard reprehensible," Biden said. "It is a dangerous attack on a vital pillar of democracy ... undercutting the legitimacy of a judge by suggesting that because of his heritage he's incapable of being fair. It is racist."
Clinton, who also has attacked Trump's comments, clinched the Democratic nomination earlier this week, according to The Associated Press.
In addition to endorsements from Biden and Obama, the former secretary of state on Thursday gained an important endorsement from Sen. Elizabeth Warren (D-Mass.).
“I’m ready to jump in this fight and make sure that Hillary Clinton is the next president of the United States and be sure that Donald Trump gets nowhere near the White House," Warren said.
This article has been updated to include additional comments from Biden.