Jets coach Phil Stubbins confirmed that Neumann has signed a two-season deal after Adelaide United agreed to release Neumann, with a season to run on his contract.
With Neumann, 28, due to arrive on the Hunter next week, Stubbins said: "Jeronimo has been on our radar for a while and there have been too many good things said about the kid as a player, and also as a persoanlity, for us not to be interested.
"He can score goals and make goals and we have said all along we need more goal power at the club.
"He gives us more amunition up front and is a real livewire. He is somebody I see more as a second striker for us but having said that he has proved he can play in various roles and still be effective.
"He ticks a lot of boxes and as a player fits into the culture we are trying to establish here."
Jeronimo said he is looking forward to linking up with his new team-mates.
"Phil (Stubbins) contacted me to tell me the ideas he had for the club and I was excited to be part of it,” Jeronimo said.
"My job is to score goals and give 100 per cent for the team every time I am on the field, so hopefully myself and my teammates can help Newcastle finish in a strong position on the table.
"I am very happy to join the Jets and I'm looking forward to getting started and doing my best for the fans."
An Adelaide United source declared that discussions over a proposed move had been "on-going for some time", explaining: "It's not the club's policy to stand in the way of a player who can legitimately establish a longer term future elsewhere and this is where we find ourselves in relation to Jeronimo."
Adelaide coach Josep Gombau thanked Jeronimo for his service to the club.
"Jeronimo is a player that helped the team a lot in his time here," Gombau said.
"I want to say thanks for all his efforts and what he put into the team."
Part of the agreement is that Jeronimo will play his final game for the Reds against Málaga on Friday 25 July at Adelaide Oval.
Neumann, who joined Adelaide in August 2012, made an indelible impression at Coopers Stadium, scoring 17 goals in 53 appearances and catching the eye with some superb strikes and an ability to improvise in tight situations.
He is just the latest capture for the Jets, who earlier this week announced the arrival of former Young Socceroos defender Sam Gallagher on a one-year deal.
Former A-League player of the year Marcos Flores, Northern Ireland international Jonny Steele, former Socceroos defender Adrian Madaschi and attacking midfielder Joshua Barresi have also been added to the playing group since Stubbins took the helm.
"As a club we struggled over the last few years. We have over 10,000 members who have supported the club through those barren times and we are doing everything in our power to bring some smiles to their faces next season," Stubbins said.
"It's going to be a tough campaign, a lot of clubs have been investing heavily and we don't want to be left behind."