The versatile player will return from a long stint in Scotland aiming to impress in his home state, having liked what he saw from the Reds last term
McGowan, 22, was released by financially stricken and relegated Heart of Midlothian at the end of the 2013-14 campaign but did not stay on the market for long, with the versatile player - able to play in midfield and defence - committing his future to the Coopers Stadium for the next two seasons.
Brother of Socceroo Ryan McGowan, the Reds' most recent acquisition was swayed to return to South Australia after watching his hometown club play some impressive football under their Spanish coach.
"Being an Adelaide boy, I've always been an Adelaide fan so I paid close attention to the team," he said in a club statement.
"Last season I watched a lot of games where the coaching and playing staff were really exciting and bringing a new brand of football to the club, I just wanted to be a part of it.
"Gomabu's style and philosophy that he brought in is widely praised and it's one of the main reasons I signed. And the league as a whole is improving. It's on par with Scotland and probably playing better football. So as soon as the opportunity arose, it was a pretty easy decision."
Gombau meanwhile hailed the capture of McGowan as another step in the right direction for the club.
"He is a strong, athletic and young player with good experience in Europe and at an international level," he said.
"I know he can help us in our back four as well as in midfield. He's a well-rounded player, which isn't always easy to find.
"We are also bringing back home a South Australian player, which follows our vision in having SA players playing for Adelaide United."