Kidman said she knew Urban was "the one" when he surprised her with flowers on her birthday.
"He sat on the stoop of my New York apartment. I came out 5:00 a.m. in the morning, and it was my birthday and he had flowers," Kidman said. "And that was it. I was a goner. I'm like, 'Yes, I'll marry you.'"
Kidman and Urban married in June 2006 and have two daughters together, Sunday Rose, 13, and Faith Margaret, 10. When asked on The Tonight Show if she and Urban had an anniversary party, Kidman said she doesn't like surprises.
"I mean, I don't mind a surprise, like something kind of sweet, but I don't like a surprise party," the actress said. "I had a surprise party once and I broke out in a cold sore on the spot from the shock."
"I literally did. It was too stressful," she added. "It was like I was seeing -- It was apparitions. It was bizarre. I didn't like it at all."
Urban shared a photo on Instagram of himself embracing Kidman to mark their wedding anniversary in June.
"Happy anniversary babygirl!!!!!!! my life started when you said 'I do' 5475 days ago today," he captioned the post.
Kidman was previously married to Tom Cruise and has two children, daughter Isabella Jane, 28, and son Connor, 26, with the actor.
Kidman most recently starred on the Hulu series Nine Perfect Strangers, which concluded Wednesday. Urban released a new song, "Crimson Blue," for the show earlier this week.