The young striker has joined the Exiles for a month.
He is with them until October 15th.
Malky Mackay told the official website: "The loan move should allow Nat to gain some much needed first-team experience.
"I'm sure he'll do well for Newport over the next month and they'll see what a good young prospect Nat is.
We'll keep a close eye on him while he's with Newport and look forward to welcoming him back in to the Cardiff City fold on his return. Hopefully he can make the most of the opportunity and gain from the experience."
Jarvis scored his first senior goal in Cardiff's 3 - 1 win at Oxford in the Carling Cup last month.