After Buttigieg lauded him and urged his supporters to back the former vice president, Biden took the mic and compared the 38-year old former mayor of South Bend, Indiana, to Beau Biden, his late son and someone who the former vice president refers to as his "soul."
"I don't think I've ever done this before, but he reminds me of my son, Beau," Biden said, with Buttigieg looking on.
The former mayor lowered his head at the comment, seemingly taken aback by the power of what Biden was saying.
"I know that may not mean much to most people, but to me, it's the highest compliment I can give any man or woman," Biden continued.
Beau Biden, an Iraq War veteran and the former attorney general of Delaware, died in 2015 after a lengthy battle with brain cancer.
Joe Biden has reflected about the impact Beau's passing had on both his political and private life and he often refers to his late son as "his soul."
"The way I've been able to deal with when my wife was killed and my daughter was killed and then my son died, I've only been able to deal with it by realizing they're part of my being," Biden said with tears in his eyes during a CNN town hall in South Carolina.
Biden, at the same event, reflected on how his son had urged him right before he died to stay engaged and not retreat into himself. Biden said that every day he wakes up and "I ask myself, I hope he's proud of me today."
Buttigieg ended his campaign on Sunday and endorsed Biden on Monday.
"I am looking for a leader, I am looking for a president who will draw out what is best in each of us," Buttigieg said in Dallas, Texas, on Monday. "And I'm encouraging everybody who was part of my campaign to join me because we have found that leader in vice president, soon-to-president, Joe Biden."
Buttigieg, too, understands loss. His father, Joseph, died in January 2019, just as the former mayor's campaign for president was getting started. An emotional Buttigieg, during the Sunday night event where he ended his campaign, thanked "my father who left us just as this was getting all underway but who is very much here and part of this effort."
Biden returned to comparing Buttigieg to his late son at the end of the Monday event, and even said he was "sorry to talk about my son, Beau, so much, but he was my soul."
"I look over at Pete during the debates and I think, you know, that's a Beau," Biden continued, "because he has such enormous character, such intellectual capacity and such a commitment to other people and folks, I can't tell you how much it means to me that he would step up and endorse me."
Biden ended with a nod to Buttigieg's potential.
"I just can't tell you how much I appreciate it," he said, "because I promise you, you're going to end up over your lifetime seeing a hell of a lot more Pete than you are me."