Dortmund youngster Felix Passlack joins Hoffenheim on a two-year loan deal as part of the agreement, with the Black-Yellows hoping regular first-team football will further the 19-year-old's development.
Toljan a versatile signing for Der BVB
Dortmund's sporting director Michael Zorc told bvb.de that Toljan is a player who "can slot in on both the left and right of defence", and described the 23-year-old as "one of the cornerstones of the side that secured the title for Germany at the U21 European Championship this summer."
The man described by Zorc as "a player with great potential" played every minute of Germany's five matches at the 2017 UEFA European Under-21 Championship, including the final against Spain in which he assisted Mitchell Weiser for the only goal of the game.
He was also a key figure in Germany's march to the final during the 2016 Olympic Games, although they lost to Brazil 6-5 on penalties and took home silver as a result.
The Stuttgart-born defender appeared for the Swabians' under-17 side before moving to Hoffenheim in 2011, where he would go on to appear for the under-19 and reserve teams before making his senior debut against Mainz 05 in October 2013.
He went on to make 63 appearances for achtzehn99, scoring twice, and was an integral part of last season's historic fourth-placed finish.
Youngster gets his Bundesliga opportunity with loan move
Right-back Passlack goes the other way as part of the deal with Zorc saying the club hope that "Felix is able to have as much playing time as possible" at Hoffenheim, adding that they "believe he is in good hands with Julian Nagelsmann."
The 19-year-old has appeared five times for Germany's under-19 squad and has made 21 first-team appearances for Peter Bosz's side since his debut against SV Darmstadt in February 2016.
He can also be deployed as right-sided midfielder as well as being fully capable on the left and right side of defence, but will likely fill the void left by Toljan at his new club.