The 20-year-old singer had apparently been dating the Hungarian model since last year. The pair decided to call it quits as their hectic schedule was making it difficult for them to continue, reported Contactmusic.
"There was no big fall out, things just fizzled out as Niall and Barbara are both working in different parts of the world," a source said.
"They are both really busy and Niall is focused on recovering and getting ready for the band's massive Where We Are tour. They are still in touch and friendly," the source added.