The boyband were making an appearance on popular US daytime show, Good Morning America, when they were quizzed about their relationship status.
When asked by the show's host Robin Roberts who in the band was "still available", Harry and Niall raised their hands.
Their confirmation received enormous cheers from the crowd, who had gathered to see the boyband perform in New York's Central Park.
The news also came as a relief to some, after Harry was spotted enjoying dinner with reality star Kendall Jenner in Los Angeles last week. Harry is known for having his way with the ladies and speculation was rife that he may have wooed Kendall with his charm.
Meanwhile, Irish heartthrob Niall has been linked to this year's X Factor contestant Tamera Foster.
On ITV2's Xtra Factor, it was revealed that the pair have been direct messaging each other on Twitter, but Tamera claimed that Niall has just been offering "some constructive criticism".
While Harry and Niall are single, the remaining members of 1D are off the market. Liam Payne is dating old school friend Sophia Smith, while Louis Tomlinson is in a long-term relationship with girlfriend Eleanor Calder. Also, Zayn Malik is engaged to Little Mix singer Perrie Edwards.
One Direction appeared on GMA to promote new tracks from their album, Midnight Memories, and to reveal dates from their upcoming tour, 'Where We Are'.
Watch One Direction's music video for 'Story Of My Life' below: