Talking to the Daily Star, the rapper said: "Harry doesn't need any help with exposure, everybody in the world knows who he is."
The 46-year-old has previously mentored Rihanna, Kanye West and Rita Ora.
Jay Z's comments follow four new songs being registered to a performing rights organisation in the US under Harry's name.
The Roc Nation founder said he'd be happy to work with the singer but pointed out the hardest step in Harry's solo career will be "to make the transition from being part of a group to becoming an individual artist".
He added: "I can get him working with the bigger artists, the biggest producers and have him as the biggest artist in the world."
The singer's new tracks - which are called Already Home, Coco, Endlessly and 5378 Miles - appear on the American Society of Composers, Authors and Publishers (ASCAP) website with Harry Styles listed as the only performer.
Snow Patrol guitarist John McDaid and producer Gary Go are listed as co-writers.
One Direction started their year-long hiatus on 13 December.
Since early 2014, there have been rumours Harry was planning a solo record but always denied an album was in the works while he was in the band.
He's previously worked on tracks with Kodaline and Meghan Trainor but the new songs are the first sign of him releasing his own work outside of One Direction.