The Gunners have been tracking the Brazil international since the start of the summer and their push for him has been made easier following Eddie Howe's departure as Newcastle boss.
Howe had previously refused to give any guarantees over Guimaraes' future at St. James' Park and a move to North London now looks all set, with Arsenal paying around £70M up front, followed by £10M in performance related instalments.
Mikel Arteta is hopeful of having Guimaraes in place for the final week of Arsenal's preseason campaign, after the midfielder travelled to Spain to join up with Newcastle's camp, but there is one final hurdle to cross.
After two big spending summers at the Emirates Stadium, Arsenal's hierarchy are keen to ensure more sales, to balance against major new arrivals.
Jakub Kiwior, Karl Hein and Leandro Trossard have all moved on and Arsenal want to seal Christian Norgaard's £7M move to Everton before signing off on Guimaraes.
If a deal is wrapped up in the coming days, Guimaraes could feature in Arsenal's two home-based friendlies against Borussia Dortmund and Como, before the FA Community Shield vs. Manchester City on August 16th.