The 27-year-old is set to join the Gunners in a dramatic deadline day switch from the Spanish capital to north London.
Partey has been a leading target for Mikel Arteta throughout the window, with the Gunners knowing that they only needed to trigger his £45m release clause to push through a deal.
However, the club have been desperately trying to balance the books before moving for Partey and the club are expected to offload the likes of Sead Kolasinac, Sokratis and Matteo Guendouzi before the window closes.
That has convinced the club’s board that they can finance a move for Partey and given the midfielder’s situation he has already agreed a contract with the club.
According to the Guardian, Partey will earn around £250,000-a-week with the Gunners and that represents a significant boost on his £60,000-a-week wages at Atletico.
It’s claimed the club have also agreed to pay Partey’s representatives a seven-figure sum.
Given Arsenal have spent four seasons outside the Champions League, it is a significant investment in the midfielder, who has just turned 27.
Arsenal had hoped to sign Lyon playmaker Houssem Aouar but the Frenchman decided to stay with the club for an extra season.
The club announced his decision on Friday, leaving Arsenal with 72 hours to switch their attention to Partey.
Partey is expected to undergo a medical in Madrid.