As The Mercury first reported earlier this week, coach Brian Goorjian fended off interest from several rival clubs to secure the 23-year-old.

Adel played 19 games for the Cavaliers in the 2018-19 NBA Season, starting three and producing played a career-high 36 minutes for the Cavaliers against the Washington Wizards in February 2019.

The Melbournian most recently played for the Long Island Nets in the NBA G-League after signing with contract with their NBA affiliate the Brooklyn Nets.

He was averaging 11.1 points, 4.2 rebounds, and 2.7 assists per game for Long Island before the season was cancelled due to COVID-19.

Adel also played for the Canton Charge (12.1 points and 6.1 rebounds per game) and Raptors 905 (12.5 points and 5.5 rebounds per game) in the NBA G-League in the 2018/19 season.

Born in South Sudan, Adel was raised in Melbourne before moving to the US where he played at the University of Louisville for three years, averaging 11.2 points, 4.2 rebounds and 2.0 assists in 26.8 minutes per game across 89 appearances.

It's the biggest name thus far revealed since NBL free agency opened, with Goorjian confident time with Illawarra can propel the star back to the NBA.

"Deng is an NBA level talent and at just 23-years-old, he holds aspirations to make the NBA again," Goorjian said.

"The fact he has put his trust and faith in the Hawks program to help him on that journey is a great endorsement of the organisation and its direction under new ownership.

"On the court Deng is going to help tremendously as we construct a roster that will help establish a winning culture for the club."

Adel joins Emmett Naar, Deng Deng, Dan Grida and Sam Froling on the Hawks roster, with Cam Bairstow expected to be added in the coming week.

"I'm super excited. I wanted to join the Hawks, it's a great situation there having Coach Goorjian and the ownership group they have," Adel said.

"It's an opportunity to build a new culture there and I'm excited for the challenge. I've seen a couple of the [Hawks] games on YouTube and seen how wild the crowd gets.

"[Having Goorjian as coach] was a big factor. I'm trying to develop my game and I want to grow every year and I think the resume that he has speaks for itself.

"I want to be in that type of environment where I can work every day and be challenged by the coach and a coach that is willing to put himself out there for the betterment of the players."