The US actor, who plays Will Schuester in the TV show, was recently seen leaving club Bardot with Diaz and the rumours soon started that they are dating.
Asked about the hook up, Morrison said to E! Online that they are 'just friends'.
He also revealed what he thought about Gwyneth Paltrow, who is set to appear on the hit show.
Morrison said: 'Dare I say I have a crush on Gwyneth Paltrow? She's the most lovely... She's not like a movie star, she's just like a normal person.
'She was so awesome to work with. She's so talented. She's singing a lot, like three numbers or something.'