The 33-year-old British royal lauded his mother, who died at age 36 in 1997, while attending the Obama Foundation Summit with former first lady Michelle Obama on Tuesday.
Prince Harry said in a conversation with Ariel Investments president Mellody Hobson that his military service and Princess Diana inspired his passion for giving back. He also explained why he thinks his mom was called the "People's Princess."
"I think she had a lot in common with everybody but also she certainly listened in a very, very short space of time," the prince said. "In society we suffer from this illusion of this reality where some problems get so big that nobody wants to get involved. She was the one that changed that."
"I will always look up to her as being my ideal role model," he added.
Prince Harry and Obama surprised students at Hyde Park Academy in Chicago, Ill., ahead of the summit. Kensington Palace said the high school is located across from "the future site of the Obama Presidential Center."
"Thanks to my friend Prince Harry for joining me today to surprise these remarkable students at Hyde Park Academy on the South Side. We were blown away by their passion, ambition and talent! #ReachHigher #ObamaSummit," Obama captioned a slideshow of photos on Instagram.
Prince Harry and Obama have previously collaborated on other causes, including the Invictus Games.