The One Direction heartthrob ended his brief romance with Irish model Zoe Whelan in July and has recently been linked to singer Ellie Goulding, however, it's thought the 20-year-old star has secretly reunited with his former flame.
A source told heat magazine: "Niall wants everything kept completely under the radar as he feels they simply won't survive if they're being watched. But the truth is, he's mad about her and when he's in Ireland
they're spending almost every second together."
Niall was so besotted with his 18-year-old girlfriend he invited her as his date to brother Greg's wedding in March. But the budding relationship is thought to have crumbled under the strain of his band's busy 'Take Me Home' world tour earlier this year.
However, Zoe has reportedly been jetting in from Ireland to meet Niall in recent months and she is friends with the hunk's bandmates, Zayn Malik, Liam Payne, Harry Styles and Louis Tomlinson.
The source explained: "She's flown out on four different occasions to meet him over in London and be close to him. Although they would prefer to keep the relationship quiet, they actually get to hook up together a lot more than you'd think and Zoe is a regular face backstage at their gigs."