Demi 20, and Niall, 18, apparently dined at the Pink Taco Restaurant after the show and were alone for the eating experience, according to website UsMagazine.com.
The two musicians have been rumoured to be dating after she admitted in an interview earlier this year she thinks he is ''adorable.''
In June, Niall's bandmates picked 'The X Factor' USA judge as his perfect match during a round of 'Rapid Fire Romance' on etalk.
Harry Styles teased: ''Niall dreams dirty things!''
Demi won a prize at the MTV VMAs for Best Video with a Message for her song, 'Skyscraper'.
One Direction took home three awards for Most Share-Worthy Video, Best New Artist and Best Pop Video for 'What Makes You Beautiful'.
Niall thanks fans for the accolades on twitter following the event.
He posted on the micro-blogging website: ''Guys what the Hell! You are incredible, 3 VMAs! We love you all so much! All 3 of them are for you! Thank you!''