Aberavon are currently bottom of the Principality Premiership with one win from their six league games so far this season.
"I am glad to be back at the Wizards and I am relishing the challenge ahead," said Hyatt, who takes over after Simon King left the club by mutual consent last week.
"I'm immensely proud to coach Aberavon where I have so many great memories from my playing days. Aberavon has a great history, great people behind the club and the best supporters in the league. With hard work from the coaches and players, we aim to rise to the challenge ahead.
"So let's have a big crowd at the Talbot Athletic Ground this Friday when we face Bridgend because your vocal support drives the boys on!"
Aberavon's clash with Bridgend on Friday evening kicks off at 7.15pm.