The 'California Gurls' singer told The Graham Norton Show that she had to put on a brave face on stage, despite turmoil in her personal life.
"I went through some pretty tough times last year," she explained, referring to her split from comic Russell Brand. "[But] I know my problems are my problems. They are not the audience's problems.
"They are here to see a show and to be entertained so I got on that lift, put a smile on my face and went up [on stage] with my t*ts spinning!"
Perry appeared on the show with Cheryl Cole and Ross Noble as part of the promotional tour for her film Katy Perry: Part of Me.
Earlier in the week, she surprised fans by turning up at a preview screening of the 3D feature.
Watch the trailer for Katy Perry: Part of Me below: