The rugby star said during a photo shoot with Men's Health that he was blown away to be dating the girl that everyone "had posters of... on their walls".
"The whole 'be confident in yourself' thing is cheese," he said. "Let's be honest - if a girl is gorgeous, it's overwhelming.
"It definitely was when I met Kelly because every guy had posters of her on their walls when I was growing up."
Evans also shared his advice for plucking up the courage to ask out beautiful women, saying: "If she speaks to you and she's down-to-earth, then you're fine.
"If she's not, you've saved yourself a lot of hassle. If she's down-to-earth and attractive, it's just a matter of where to sign."
Brook previously described Evans's down-to-earth demeanour as "refreshing".
The full interview appears in the November issue of Men's Health, on sale Monday, October 1.
Thom Evans is represented by Select Model Management.