The animated group - created by Blur star Damon Albarn and artist Jamie Hewlett - were apparently approached by the 'I Kissed A Girl' singer who asked to collaborate with them on a song for their new album 'Plastic Beach'.
But they turned her down because of her engagement to the British funnyman.
Bassist Murdoc Niccals said: "Katy Perry - she's been after a guest spot for ages and I tried to turn her down.
"No, I couldn't work with the woman while she's got Russell Brand all over her."
He joked to BBC 6 Music: "I wouldn't invite anybody that I didn't admire. There are lots of different methods to get this sort of talent on this sort of record. One way is you can phone them up and ask them. That's one way.
"The Gorillaz name goes a long way now. Much further than it did at the beginning. Now, it gives you carte blanche really. You can ask whoever you like. Some people will just agree on the back of that. Others take a little bit more persuading."
Gorillaz new album 'Plastic Beach' is released on March 8.