The singer takes over from Beverley Knight, who currently plays the role of superstar Rachel Marron, in June.
She said: "I couldn't be more excited about joining the cast of The Bodyguard and to play the iconic role of Rachel Marron will be a dream come true. I am a massive Whitney Houston fan so to be given the opportunity to play a role made famous by her every night will be a real privilege. I start rehearsals very soon with my fellow cast mates and the brilliant creative team and, with a little trepidation, I am looking forward to our first performance in June."
The show, based on the hit 1992 film which starred Kevin Costner in the title role, runs at the Adelphi Theatre until the end of August.
The film gave Houston one of her biggest hits - a cover version of Dolly Parton's I Will Always Love You - which became one of the biggest-selling singles of all time.