The 23 year-old has signed a contract until 2018, joining the club at the beginning of July and will replace Timo Hildebrand in the side's squad.
The shot-stopper has had a wonderful season in the 2nd tier of German football with 30 appearances and 9 clean sheet over the course of their league this season.
Schalke will be able to reinforce their squad further after announcing the signing of Giefer with the club securing the all important Chamions League group stage after finishing 3rd on the table at the conclusion of the league at the weekend.