The 25-year-old has returned to his homeland after faling to establish himself in East Yorkshire since joining the club just under a year ago.
Mayer found himself out of favour from early in the new year, with his last start coming in the EFL Trophy game against Fleetwood in January.
All told, the Austrian made 14 appearances in all comeptitions last season and was afforded just one start in the league among six League One appearances.
Despite falling down the pecking order, Mayer insists that he will recall his time at the club with fondness.
He said: “I really enjoyed playing for the Tigers. It hasn’t worked out for me but that’s football and I’d like to say thank you to everybody – the staff and my team.
“I worked hard every day and gave my best to make my boys better, and myself better. I was really pleased we got promoted.
“Hull will always be a part of my heart and I hope the team do very well this season and in the future.”