The 43-year-old actor managed to creep up behind the singer as she sang a tune from her upcoming album, "Smile", and she was clearly terrified when she spotted Bloom.
"You're not supposed to see me doing this," Perry said as she screamed before laughing uncontrollably.
As the 35-year-old caught her breath, Bloom playfully said hello to all those watching at home.
Perry revealed she was "literally sweating" from the shock and added, "He's not supposed to see me like this."
She added, "I'm not embarrassed, but it's like, you know, when you're doing something in your room and somebody walks in and it's like, 'This is my alone time!' "
Perry, who is expecting the couple's first child with Bloom, is gearing up for the release of the deluxe edition of her new album on 28 August.