Petratos and the Jets signed off on the deal on Tuesday which ties him to the Ernie Merrick-coached side until 2019.
It is the second time in six months Newcastle has signed the 24-year-old after securing his signature in January on a three-year deal beginning at the start of the 2017-2018 season.
However, by early February the former Brisbane Roar star's deal had taken a twist, with Brisbane deciding to cash in on the attacking midfielder before the start of the AFC Champions League by selling him to K-League side Ulsan Hyundai.
The Jets received compensation of $150,000 after the sale of Petratos, but have signed the player anyway after his contract was mutually terminated eight games into his time with the K-League club.
“I am very happy to join the club,” Petratos said.
“Through the media I have been following the Jets and just seeing what’s been happening over the past few months is very exciting.
“I’m looking forward to meeting the boys officially and to be in the team with them. I’ll work hard and play my part in the team, but two things I know I am here for are to assist and score goals.”
Petratos will unite with his brother Kosta in Newcastle, who has signed a one season deal with the Jets, as well as other off-season signings Daniel Georgievski, Glenn Moss and Roy O'Donovan.
Jets coach Ernie Merrick noted Petratos was an "exciting player and a terrific signing".
"Dimi is an attacking midfielder who is confident on the ball, can retain possession and play key forward passes to strikers," Merrick said of Petratos, who has scored 19 goals in 124 A-League matches.
"I hope to add to his game and encourage him to push more often into goal scoring areas."
