Couric wrote a first-person story for InStyle magazine on Friday in which she remembered back to Aug. 31, 1997, when she was at her home in New York and heard that Diana, who was 36, died in a car crash in France while her driver was trying to escape the paparazzi.
"I’ll never forget where I was when I heard that Princess Diana was critically injured in a car accident in Paris,'' she wrote. "My husband, Jay, was in the middle of his battle with colon cancer, and it was an incredibly stressful time.
"When the news broke, I spent hours glued to the TV in our family room, waiting for any bit of information. I was so upset and holding my breath like the rest of the world. But eventually, Brian Williams announced she had died. I was devastated."
Couric's husband, Jay Monahan, died at 42 of colorectal cancer less than a year after Diana's death.
"Although I was reporting on what was going on, I too was mourning Princess Diana,'' Couric wrote. "And at the same time, I kept imagining what would happen if my husband died from the cancer that had taken over our lives."
Diana's death left her two sons, Prince William and Prince Harry, without a mother. They were 15 and 12 at the time.
"The young princes made me think of our own young daughters and what losing a parent might mean for them. At one point, the producers had to take the cameras off me, because I was so choked up and tears started to stream down my face."
Couric covered Diana extensively on TODAY, but didn't get a chance to meet her until just a year before her death, at a luncheon in Chicago.
"I was nervous to meet Princess Diana and was seated two seats away from her at lunch,'' she wrote. "We chatted and she told me she liked my pink lipstick. Funny. Then I said something like, 'You must be exhausted traveling and meeting so many people and having to shake hands with all these strangers. Are you excited to go home?'
"I will never forget her response: 'I would be, but I’m going home to an empty house.' This was as she was finalizing her divorce from Prince Charles, and she seemed a bit melancholy and lonely," Couric wrote. "My heart broke a little for her. 'Why don’t you invite some friends over and have a slumber party?' I playfully suggested. She just tilted her head and looked at me quizzically."
Couric remembered Diana wearing her "insecurity and vulnerability" on her sleeve, which endeared her to millions.
"Yes, she was a princess, but somehow, she was like all of us,'' Couric wrote.
Prince William, 37, opened up in May about the struggle of losing his mother when he was 15 for a BBC documentary about mental health.
"I've thought about this a lot, and I'm trying to understand why I feel like I do, but I think when you are bereaved at a very young age, any time really, but particularly at a young age, I can resonate closely to that — you feel pain like no other pain," William said. "And you know that in your life it's going to be very difficult to come across something that's going to be even worse pain than that."
William and Harry have kept their mother's memory alive by continuing to support many causes that she championed.
"Diana was keenly aware of her place on the world’s stage and seemed to want to make the most of it,'' Couric wrote. "I see this legacy living on through her sons — not only in the relentless media scrutiny they endure, but also in how they use this attention to advance causes that are important to them."