Philbin, who cohosted "Live! with Regis and Kathie Lee" alongside Gifford for 15 years, died over the weekend at the age of 88.
Appearing from her Connecticut home on "TODAY," Gifford revealed she had just seen Philbin two weeks ago, after inviting him and his wife Joy over for what she even sensed at the time would be the last time she ever saw him.
"I saw Reeg get out of the car with Joy and I sensed much more fragility since the last time I saw him in January in Los Angeles," she said. "We always just picked up right where it picked off. It's been 20 years since I left the show and we've been dear friends in the years since then."
"We had the best time and after they left, I thought to myself, 'Lord, is that the last time I'm going to see my friend?' Because he was failing, I could tell," she explained.
Gifford revealed she visited Joy and his children after his death on Sunday, as they all went through photos together and reminisced.
"I didn't want to intrude on their private family time," she added, saying she could relate after losing husband Frank Gifford in 2015. "You love your friends reaching out, but you also desperately need that private time as a family. I was just grateful to have that time with them, comfort them a little bit, let them know I believed with all my heart I know where Regis is and I know who he's with, because I had many many conversations with him over the years about faith, about where we go when this life is over and he was very curious as always, listened."
She went on to say the two "never had any cross words" with each other during their decades-long friendship and called him "the most grateful person in the world."
Gifford got emotional as she was asked what she'll miss most about him.
"Everything," she said, tearing up. "I'm just so grateful the Lord gave me that final time and it was so precious, because when I talked to Joy the day after he had passed, she said, 'Kathie, he hadn't laughed in a long, long time. I was so worried about him.'"
"He was like Frank, just ready. And so many of his friends had died, he was ready to go and [Joy] said, 'The day we came to have lunch with you was the last time I heard him laugh,'" she added. "That will forever be a precious gift the Lord gave me, that I got to laugh again with one of my best friends in all my lifetime."
Regis and Kathie Lee hosted "Live" together from 1985–2000, before Gifford left the show and was replaced by Kelly Ripa. Philbin and Ripa cohosted for another 10 years before he left the show in 2011.