The 26-year-old joins for free after leaving Hannover96, where he played under Reds head coach Daniel Stendel. The length of the contract for the former Austria under 21 player is yet to be revealed.
Radlinger, who is six foot five, joins fellow new goalkeeper Brad Collins, who was brought in last week after leaving Chelsea.
The Austrian began his career at Ried then spent eight years with Hannover who loaned him out to Rapid Vienna, Nuremberg and Norwegian club Brann.
The only first team matches he played for Hannover came when Stendel was manager during the 2016/17 season in the Bundesliga 2.
He is the fourth new face to arrive at Oakwell this summer following Collins, Danish defender Mads Andersen and winger Luke Thomas.