The test, which involved a pinprick and took about a minute, was performed at Guy’s and St. Thomas’ Hospital in London. The 31-year-old prince tested negative for HIV.
Harry, who admitted to some nerves, said he took the test "to show how easy it is to get tested."
He added, "It's amazing how quick it is."
Diana famously championed AIDS awareness in her life and was one of the first major figures to work to destigmatize AIDS and HIV.
Kensington Palace announced last month that Harry would be devoting a significant amount of his charitable work to HIV awareness to carry on his mother's legacy.
He told viewers watching the Facebook live broadcast, "Gay, straight, black, white, ginger, whatever — why wouldn’t you just have a test?"
"We all shouldn’t be on the other side of the river saying, 'You should get the test,'" he said. "It should be normalized. Everybody should get it."