The MLB superstar took his wife to see the guys at Planet Hollywood in Vegas over the weekend -- and not only got her backstage for a meet and greet ... but, had the guys take her on stage for a 5-on-1 serenade!
Check out the video as Kayla Harper gets a flower and a special rendition of "Shape of My Heart" from AJ, Howie, Nick, Kevin and Brian!
After the show, Kayla wrote, "My 9 year old self lost her mind last night. Bryce has been surprising me with little gifts all week and one of them happened to be a black dress that he said I needed for Sat night."
"He let me know at dinner that he was taking me to see the Backstreet Boys... little did I know, the biggest surprise of them all was meeting them & then having them pull me onstage to be serenaded."
So, how much did it cost? Doesn't matter to Bryce -- who's expected to sign a contract that could be worth hundreds of millions of dollars!