"It is with broken hearts that Hallie, Hunter, Ashley, Jill and I announce the passing of our husband, brother and son, Beau, after he battled brain cancer with the same integrity, courage and strength he demonstrated every day of his life," the vice president said in a statement late Saturday.
"The entire Biden family is saddened beyond words. We know that Beau's spirit will live on in all of us, especially through his brave wife, Hallie, and two remarkable children."
President Barack Obama said he and the first lady were grieving alongside the Biden family.
"Michelle and I humbly pray for the good Lord to watch over Beau Biden, and to protect and comfort his family here on Earth," Obama said.
The younger Biden was a lawyer, member of the Delaware National Guard and former Delaware attorney general.
He was hospitalized earlier this month at Walter Reed National Military Medical Center. The vice president's office had declined to say what he was being treated for.
In 2010, Beau Biden suffered a mild stroke. Three years later, he underwent surgery at a Texas cancer center to remove what was described as a small lesion.
He announced last year that he would not seek a third term as attorney general and instead planned to run for governor in 2016.
Full Statement by the Vice President and his family:
"It is with broken hearts that Hallie, Hunter, Ashley, Jill and I announce the passing of our husband, brother and son, Beau, after he battled brain cancer with the same integrity, courage and strength he demonstrated every day of his life.
The entire Biden family is saddened beyond words. We know that Beau's spirit will live on in all of us-especially through his brave wife, Hallie, and two remarkable children, Natalie and Hunter.
Beau's life was defined by service to others. As a young lawyer, he worked to establish the rule of law in war-torn Kosovo. A major in the Delaware National Guard, he was an Iraq War veteran and was awarded the Bronze Star. As Delaware's Attorney General, he fought for the powerless and made it his mission to protect children from abuse.
More than his professional accomplishments, Beau measured himself as a husband, father, son and brother. His absolute honor made him a role model for our family. Beau embodied my father's saying that a parent knows success when his child turns out better than he did.
In the words of the Biden family: Beau Biden was, quite simply, the finest man any of us have ever known."
Full Statement by the Delaware Governor Jack Markell:
"Carla and I are heartbroken for Hallie, his children, his parents, his siblings, and the entire Biden family. Beau spent his entire career in the service of his country and his state. He was an outstanding Attorney General, lawyer, soldier, and father. I feel privileged to have served with him and Delaware is a better place thanks to him.
"Beau was also a friend. He was unfailingly interested in the well being of Carla, my kids and my extended family. My entire family is shattered by his death.?"
In honor and remembrance of Beau's life, the Governor has directed that the U.S. and Delaware flags be flown at half-staff.
Reaction to death of vice president's son Beau Biden
By The Associated Press------
"Michelle and I humbly pray for the good Lord to watch over Beau Biden, and to protect and comfort his family here on Earth." -- President Barack Obama.
"He was extraordinarily in tune with people. He was passionate about serving. ... I think it's important that people know what a real, genuine, decent guy he was." -- Democratic Delaware Gov. Jack Markell.
"Throughout his life, Beau never shied away from doing the right thing, even when it meant doing the hard thing. Beau served his country and community with honor, and that's how he will be remembered." -- U.S. Sen. Chris Coons (D-Del.).
"I first met Beau when he was six years old. ... It's been a privilege to watch him grow up and become a leader in our state and in the Delaware National Guard. My last memory of Beau was during the Return Day Parade in Georgetown, Delaware, two days after last November's election. I was walking along the parade route shaking hands with people just as Beau passed by, standing in a National Guard vehicle, waving at the crowd. For a moment, our eyes met, he waved to me and I to him. Then, he mouthed these words to me, `I love you.' I smiled and returned them to him. And, he was gone." -- U.S. Sen. Tom Carper (D-Del.)
"Beau had a warm and generous spirit. He was a truly giving person, and he appreciated the good in others in the way we all should. He leaves a legacy of service, and also a great personal legacy that calls on each of us to be more gentle in our judgments and more gracious with our thanks. He was one of the best of the good guys." -- U.S. Rep. John Carney (D-Del.)
"He was filled with a sense of honor, duty, and humility - to the core. He was a class act, period, ingrained with integrity, compassion, a sense of moral obligation to help others, and especially people who were hurting." -- Secretary of State John Kerry.
"Beau's dedication to public service was deep, broad and profound. He embodied the best and most noble traits that his parents sought to instill in him. I know Joe is very proud and he should be proud because Beau was simply a joy to know." -- Democratic Senate minority leader Harry Reid (D-Nev.).
"Tonight, our country lost a committed public servant, someone who devoted his own life to making the lives of others better. Beau was steadfast in his defense of our principles, whether as a member of the Delaware National Guard or as the state's Attorney General. ... I had the privilege of knowing Beau personally. He was a `mensch' in the truest sense of the word." -- DNC Chair Rep. Debbie Wasserman Schultz.
"My God, he's just a young man. ... It's just so difficult. ... I never heard a disparaging word about him as a person." -- Former Delaware governor and Republican U.S. Rep. Mike Castle, who many political observers expected to square off against Biden in the 2010 U.S. Senate race before Biden opted not to run and Castle suffered a stunning defeat in the GOP primary.
"As a dedicated Attorney General and soldier, Beau devoted his career to proudly serving his country and home state. It was an honor to serve alongside him as he worked tirelessly to fight for the powerless and protect the most vulnerable, our children." -- Dennis P. Williams, Democratic mayor of Beau Biden's hometown of Wilmington.
"The good die young. ... He was a rock star. ... He had a great image, great character. He was just a friendly, approachable individual." -- New Castle County (Delaware) Executive Tom Gordon, a longtime friend and political ally of Joe Biden.
"This is truly tragic news. ... Beau served his country and the citizens of Delaware with honor and dignity. He leaves behind a lasting impact on the world around him. He will be missed." -- Charlie Copeland, chairman of the Delaware Republican Party.