The "Ghost" star, 56, was about to appear on "The Tonight Show" to promote the candid "Inside Out" when Willis, 64, reached her backstage.
"I was getting ready to do Jimmy Fallon live the other night, and I was in the dressing room and my phone rang, and it was Bruce,” Moore revealed on the Netflix podcast “Present Company with Krista Smith.”
"I was prepared for there, maybe, to be some sensitivities, and he called and he got very emotional. He said, 'I'm so proud of you,'" she added.
"I, too, then became very emotional, and I’m not a crier ... the purity of his love and acceptance, the space that he could hold for me, to be walking out and (to have) that encouragement, it just really meant so much, so much to me," she shared.
The Hollywood stars were married from 1987 to 2000 and share three daughters: Rumer, 31, Scout, 28, and Tallulah, 25.
In her memoir, Moore writes honestly about the marriage. "Not everything in the book is all great. It's not horrible nor do I feel he's a horrible person," she revealed during the podcast.
As for their divorce, that's a happier story.
"It’s a funny thing to say, but I’m very proud of our divorce," Moore writes in "Inside Out."
"(The split) wasn’t easy at first," she continues, "but we managed to move the heart of our relationship, the heart of what created our family, into something new that gave the girls a loving, supportive environment with both parents."
She and Willis ended up feeling "more connected" when they were no longer husband and wife.
Moore was later married to actor Ashton Kutcher, 41, from 2005-2013.
Willis has been married to Emma Heming Willis, 41, since 2009. The couple share two young daughters, Mabel, 7, and Evelyn, 5.
Willis' heartfelt phone call wasn't the only time he's shown love to Moore as she promotes her memoir.
In September, the actor and his wife — along with Rumer, Scout and Tallulah — showed up to cheer Moore on at the book's launch party in Los Angeles.