The couple have been seen together on a few occasions over the last month, but according to Niall's One Direction bandmate Louis Tomlinson's sister, they are now officially dating.
Writing on Ask.fm, 13-year-old Félicité 'Fizzy' Tomlinson said: ''I haven't asked him, but when I was at 'X Factor' [USA, earlier this week] Alberto from security said Niall's girlfriend Barbara was here.
''Liam [Payne] said everyone has girlfriends here tonight except Harry [Styles] so yeah they're dating.''
Earlier this month Niall, 20, introduced Hungarian-born beauty Barbara, also 20, to his bandmates - which also include Zayn Malik - at a party in London.
A source said: ''The rest of the group were properly introduced to Barbara, though most of them met her briefly before. This time, though, it was as Niall's date.''
The couple were also spotted cosying up on a cinema date to see 'The Hunger Games: Catching Fire'.
An eye-witness said: ''They were laughing and joking together throughout the film, and both were dressed casually. You could tell they were comfortable in each other's company.''
Before dating Barbara, Niall was linked to 'X Factor' UK contestant Tamera Foster and British reality TV star Louise Thompson.
It was on this day (June 15th) in 1979 that Joy Division unveiled their iconic debut album 'Unknown Pleasures'.
The best Stephen King adaptations in film history.
Download Festival finally got the stunning weather it deserved, as over 100,000 fans descended with the likes of Guns N Roses, Ozzy Osbourne and...
Slaves sweat it out in the video for their latest single 'Cut And Run'; the first single from their forthcoming new release, the details of which are...
This year's winning shows were 'The Cursed Child' and 'The Band's Visit'.
They'll release 'Joy as an Act of Resistance' in August.
Filmmaker Spurlock (Super Size Me) is known for his investigative wit, but there's none of...
British pop heartthrobs One Direction became a worldwide sensation when they were thrust together on...
Niall Horan, Zayn Malik, Liam Payne, Harry Styles and Louis Tomlinson may make up the...