The 24-year-old contestant on The X Factor appeared with the rapper to sing and play guitar during Labrinth's hit 'Earthquake'.
After coming off stage, Arthur said: "That crowd was stupid. It was unbelievable. I can't wait to get out on stage on Saturday night."
According to ITV, rapper and producer Labrinth asked Arthur to appear with him after being impressed when he performed on last Sunday's show (October 21).
The site quotes Arthur as saying: "It was a totally unreal experience being on stage with Labrinth. He put on a great show and is a real hero of mine. It was a honour to be able to perform with him."
Following his performance of Sweet Dreams (Are Made of This)', presenter Dermot O'Leary asked Arthur what the experience was like, and Arthur replied: "For me, Labrinth is the complete artist and to even be in the same room with him is amazing."
Arthur then spoke directly to Labrinth, saying: "I just want to say thank you for having me, if you're watching."
Watch James Arthur perform 'Sweet Dreams (Are Made of This)' on The X Factor below:
Photo gallery - The X Factor week four live show:
Copyright: Ken McKay/Thames/Rex Features