The Argentinian struggled to get into the first team at the Donbass Arena last season following a move from his native Velez Sarsfield in July 2013, although he did manage to find the net six times from five starts, and had been linked with a move to Newcastle for most of the summer.
That has now been completed by the Magpies, who have the option to buy the 23-year-old at the end of the season.
"I am very pleased to sign for Newcastle United," Ferreyra said on the club's official website. "I like the Premier League and when I knew that Newcastle were interested in me, it was a very easy decision to make. I spoke to my friend Fabricio Coloccini, and when he told me about the club, I didn't need to think twice."
Ferreyra, who came through the ranks at Banfield and played there for four seasons before moving to Velez in July 2012, will link up with Newcastle's squad in Germany as they take part in this weekend's Schalke 04 Cup. Magpies manager Alan Pardew was delighted with his latest acquisition.
"Facundo is someone we know on a number of levels, including his friendship with (club captain) Fabricio (Coloccini)," he said. "We think he could be a big success here at Newcastle. This is a player who has played at the top level and is highly-regarded in Argentina. He has tremendous potential and hopefully he can realise that here at Newcastle United."