The 23-year-old, dressed in a green two-piece, is spending the festive period in Mexico with her boyfriend Travis McCoy lead singer of Gym Class Heroes.
However the singer didn't appear to be enjoying herself and could barely manage a smile despite her attentive beau's attempts to cheer her up.
Miserable: Singer Katy Perry didn't look n the best of moods as she took to the beach in Mexico on Christmas Day
The 23-year-old showed off her toned body in a tiny green bikini
Last week the I Kissed A Girl singer denied that she was engaged to McCoy after it was reported that he had proposed to her with a diamond ring during a holiday in France.
The 27-year-old has previously credited Perry for helping him to turn his life around during a dark period of depression.
"There was this really, really dark point about two years ago when I just hit rock bottom... and I called Katy who was in L.A. at the time and said to her, 'Do you mind coming out and keeping me company?
Perry is spending the festive period in Mexico with her boyfriend Travis McCoy lead singer of Gym Class Heroes
Why so blue? Perry's boyfriend McCoy attempts to cheer her up
'I'm not in a good state of mind right now,'' he told WENN last month.
"I honestly think had she not come, I really don't think I would be here right now.
"Without even talking, she just listened. I truly believe that she saved my life.'
Perry recently admitted that she is planning to shock her fans in 2009.
A happier Katy gets into the Christmas spirit at the Z100 Jingle Ball 2008 at Madison Square Gardens earlier this month
The star said she would keep her supporters guessing in the upcoming twelve months.
You're gonna see me with all kinds of different things,' she told the Daily Star.
'Maybe you won't expect it, but that's what I like to do - keep people on their toes.'
Perry added that she had no intention of following the trends set by established artists.
‘What's the point of being in pop if you're going to be a wind-up doll?’ she asked.
