Tom Bleasby's sing-a-long with the pop star has racked up more than seven million views on Facebook.
The pair recorded a version of "Flashlight" from the movie Pitch Perfect 2 using a karaoke app.
Tom, 18, who has never had a singing lesson, has now been approached by a record producer who has worked with Beyonce.
He said: "The past week has been crazy. My phone does not stop going off. The overwhelming outpour of support has been inspiring, thousands of messages from complete strangers telling me how amazed they were.
"It all feels very surreal."
Jessie J recorded the song, leaving gaps for fans to fill in with their own contribution using the Smule app. The two separate recordings are then played alongside one another, making it appear as though the singer and fans dueted together.
And so in the video in which Tom features, although it looks like he and Jessie J are interacting and singing together this is not actually the case.
Tom, from Gipton, said he learned his version of the song in just five minutes.
His video has been posted on the artist's Facebook page with the caption: "Have you seen this? It's amazing!!"
Tom, who is studying politics at King's College, in London, said the video has received thousands of "likes" and shares.
The former choirboy said he was now being "bombarded" with requests from record companies.
A teenager from Leeds has become an overnight internet sensation after singing a virtual duet with Jessie J.