The Reds have been in talks with the North East club, whose relegation to the Championship left Wijnaldum looking for a move, and have finally structured the deal so that it suits both parties.
The guaranteed up-front fee is believed to be around £23 million, plus £2 million in add-ons, with no players included either on loan or on a permanent basis despite Rafael Benitez's interest in signing Lucas Leiva.
The add-ons are throughout to centre around appearances and specific targets that Liverpool could achieve - with Newcastle satisfied with the clauses to agree to sell Wijnaldum despite having defiantly declared they would stick to their £27 million asking price.
With a deal now in place, Wijnaldum could have his medical and fly to join up with his new teammates within 48 hours - with Liverpool's first-team squad currently on their way to California for the first leg of their US tour.
Wijnaldum played the final 11 minutes of Newcastle's pre-season friendly draw with Doncaster Rovers on Wednesday, with some reports suggesting he had been forced to travel despite looking to engineer a move away from St James' Park.
Klopp turns to Wijnaldum after lack of movement in Zielinski and Dahoud deals
He wasn't due to feature until a late teamsheet change saw him put onto the bench, and he was greeted by a mixture of boos and cheers from the travelling supporters.
Wijnaldum joined Newcastle just 12 months ago from then Dutch champions PSV Eindhoven in a £14.5 million deal, scoring 11 goals - including one against Liverpool back in December - across his first and now increasingly likely only season for the Magpies.
The Holland international is said to have set upon a move to Merseyside to play under Jürgen Klopp and though personal terms still need to be agreed, a medical could be performed in the US with talks expected to be relatively straightforward.
The 25-year-old is sought as an alternative to Polish international Piotr Zielinski. Liverpool were in negotiations with Udinese over Zielinski for weeks, seeing an £11.75 million bid rejected, before becoming frustrated at the Serie A outfit's ploys.
Though Wijnaldum isn't the ball-playing central midfielder that Klopp initially wanted - the Dutchman best in his natural No.10 role - he has moved the goalposts after growning frustrated at the Reds' chase of Zielinski and their pursuit of Borussia Monchengladbach controller Mahmoud Dahoud.
He moved quickly to seal his signature after rumours of interest from Everton and Tottenham Hotspur and is said to have pushed the transfer ahead after speaking directly to former Reds boss Benitez, who asked Liverpool to decide whether or not to meet Newcastle's demands due to distraction in their training camp.
Wijnaldum, who can also play wide left or wide right, could potentially make his first appearance for Liverpool in their friendly against Chelsea next Thursday at the Rose Bowl in Pasadena.
The playmaker would become the Reds' sixth addition to the squad this summer, following Ragnar Klavan, Sadio Mane, Joel Matip, Marko Grujic and Loris Karius.
He adds to an abundance of attacking options for Klopp, with Wijnaldum likely to challenge with Mane, Philippe Coutinho, Roberto Firmino and Adam Lallana for one of three places behind a lone striker.