But as the American singer holidayed with fiance Russell Brand in Mexico yesterday, it appeared she had taken a red two-piece a few sizes too small for her.
Showing off her impressive figure in the bright bikini, it seemed the top could barely contain the 25-year-old's ample cleavage.
Itsy bitsy teeny weeny red bikini: Katy Perry flaunts her curves in a small string bikini as she holidays in Cabo San Lucas, Mexico
Perry and Brand, 34, jetted to sunny resort of Cabo San Lucas on Sunday after the pop star attended the Nickelodeon Kids' Choice Awards the previous night.
Quashing recent reports their six month romance was on the rocks, Perry admitted they have started to plan their wedding.
Brand proposed to Perry in India on New Year's Eve after just three and a half months of dating.
She said: 'He's a total bridezilla. He's like a freak, man. You should see - he's always, like, buying bride magazines. Every time we go out for breakfast he's like, "Can we just stop and get a bride magazine?"'
Enjoying the view? Russell Brand lies back on a lounger as Perry leans forward to talk to him
Perry said the couple are yet to set a date because she's currently working on her third album - a follow-up to her 2008 hit One Of The Boys.
She said: 'Well, I have to plan my new album, first and then I'm going to get to my wedding, But I'm really excited about that, too.
'Russell is a real match for me - in previous relationships I feel like I've just steamrolled the guy, so it's nice to find someone I can't do that to.'
The I Kissed A Girl singer is said to have already found her wedding dress -a two-piece outfit which will show off her toned stomach.
A source told Heat magazine: 'She knows her toned torso is her best feature, so she wants to show it off. She's also more than aware that her wedding photos will be seen the world over, so she knows her look needs to stand out.
'From the back, she wants to look like a traditional bride, with a very long train, but from the front, she wants a Vegas-style sequinned number with exposed skin.'
Perry is also rumoured to have asked pop star pal Rihanna to be one of her bridesmaids.
