The 'Problem' singer's confession comes after widespread speculation that she and the hip hop star - real name Sean Anderson - had been getting close.
Speaking to Telegraph Magazine, Ariana said: "He is one of the most amazing men in the whole world, and that includes my grandfather and my brother.
"I think the world of him, and he's an amazing person. That's kind of all there is to it."
Ariana and Big Sean were first linked after he contributed to her second album, My Everything, although they had remained tight-lipped on whether they were more than just friends.
Earlier this month, Ariana arrived in London amid reports that she had been caught on camera kissing Sean. The pair were riding a rollercoaster together when they apparently locked lips!
In August, US radio host Ryan Seacrest had tried to get a straight answer out of Ariana about whether she and Big Sean were an item.
But she coyly replied: "I mean, I guess, curiosity man, it'll kill you. I don't know what to say, Ryan. Why are you doing this me?"
Clearly Ariana finally feels it's time to let the cat out of the bag!
Meanwhile, Ariana's last high profile relationship was with The Wanted's Nathan Sykes last year, however they split within months.
In April, Big Sean and Glee star Nay Rivera called off their engagement five months after he had popped the question.
Since then, Naya has surprised fans by getting married to her long-time friend Ryan Dorsey.
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