Scocco joined Sunderland in January from Internacional of Brazil where he moved after helping Newell's win Argentina's "Final" championship in June 2013, his second league title with the club from Rosario after the Apertura in 2004.
"After his spell at Sunderland AFC, Ignacio Scocco will play again at Newell's and wear the colours close to his heart in what will be his third stage at the club," Newell's said on their website (www.newellsoldboys.com.ar).
Newell's said Scocco would arrive in Rosario on Friday to sign a five-year contract and would be presented to the media at their Marcelo Bielsa stadium on Saturday.
The club said they had made "an extraordinary economic commitment in the Argentine transfer market" but did not reveal the cost, although local media put it at $3.6 million to be paid in six instalments.
"Thanks to God who gave me the chance to return home... one of the happiest moments of my career," the 29-year-old with one Argentina cap said on his Twitter account (@nachoscocco32).
Scocco saw little action in Uruguayan manager Gus Poyet's Sunderland team that staved off relegation to remain in the Premier League in May. One of his team mates at Sunderland was fellow Argentine goalkeeper Oscar Ustari, who is also now at Newell's.
Scocco has also played for UNAM Pumas and Toluca in Mexico, AEK Athens in Greece and Al-Ain in the United Arab Emirates.
The Argentine league season starts on August 1.