Biden, whose late son, Beau, was a soldier who deployed to Iraq, bristled at former President Donald Trump's approach to the military during the presidential campaign, including a report that Trump once privately called American soldiers killed during World War One "losers" and "suckers."
Critics say Trump openly flouted norms of behavior in open pursuit of political support among U.S. troops, who are meant to be loyal to the U.S. Constitution - not any party or political movement.
"I will never ever dishonor you, I will never disrespect you, I will never politicize the work you do," Biden said from the Pentagon briefing room.
He added: "This is personal for me. The Biden family is a military family."
Pentagon leadership is under pressure to show progress in combating white nationalism and other extremism in the ranks, after current and former military service members were found to have participated in the pro-Trump siege of the U.S. Capitol on Jan. 6.
On Tuesday, the U.S. Navy's top admiral condemned two racist incidents involving hate symbols on warships, which sources said included a noose that was left on a Black sailor's bed.
Biden made history by naming retired Army general Lloyd Austin the first Black U.S. defense secretary. In his Pentagon address on Wednesday, Biden stressed other groundbreaking achievements by Black soldiers, from pilots who fought in World War Two to soldiers who fought in the Civil War.
"Right now, more than 40 percent of our active duty forces are people of color. Now it's long past time that the full diversity and full strength of our forces are reflected at every level of this department," Biden said.
Still, discrimination persists in the U.S. military.
Reuters was first to report last month that nearly a third of Black U.S. military service members indicated that they experienced racial discrimination, harassment or both during a 12-month period, according to a Defense Department survey that was withheld during much of the Trump administration.
During his first days in office, Biden signed an executive order that overturned a ban Trump on transgender individuals serving in the U.S. military.
Biden noted that Austin, upon taking over as defense secretary, ordered a review of sexual assault cases.
"This administration ... is dedicated to ensuring that every single person is treated with dignity and respect," Biden said.
Biden's visit, which included a tour of a Pentagon exhibition honoring Black service members, sharply contrasted with Trump's Pentagon debut in 2017. Trump used the opportunity to sign an executive order prohibiting refugees from Muslim-majority nations from entering the United States.
Still, it left many questions unanswered about Biden's approach to the Pentagon as speculation mounts about potential cuts to defense spending, the two-decade-old war in Afghanistan, future U.S. deployments to the Middle East and Asia and tensions with Iran.
Biden announced plans for a Pentagon review of strategy toward China but there was no sign for now of any shift in the U.S. approach.
Biden was accompanied by Vice President Kamala Harris, the first woman, the first Black American and the first Asian American to hold the second highest U.S. office.
Harris paid tribute to barrier-breaking Black servicemembers."They didn't just join to make history. They joined to serve," she said.