Early Bundesliga leaders BVB confirmed on Wednesday (30 August) that the 23-year-old, an Olympic silver medal winner who was also an integral part of the German squad that triumphed at the European Under-21 Championship in Poland earlier this summer, has penned a five-year contract at Signal Iduna Park through 2022.
The deal, believed to be worth just €5m (£4.6m, $5.9m), will also see teenage Dortmund midfielder Felix Passlack head in the other direction on a two-year loan.
He signed a four-year extension before departing for Sinsheim, where he will link up with a team that were recently well beaten by Liverpool for a place in Europe's elite club competition.
"Jeremy can slot in on both the left and right of defence," Dortmund sporting director Michael Zorc said of the addition of Toljan. "He was one of the cornerstones of the side that secured the title for Germany at the U21 European Championship this summer."
On Passlack, he added: "We hope he gets as much playing time as possible in Hoffenheim and believe he will be in good hands with TSG coach Julian Nagelsmann."
Peter Bosz's Dortmund have certainly been busy in the transfer market of late, with Emre Mor joining Ousmane Dembele in moving to Spain after completing a switch to Celta Vigo. Matthias Ginter also departed for Borussia Monchengladbach, while Andriy Yarmolenko has joined along with Omer Toprak, Mahmoud Dahoud, Dan-Axel Zagadou and Maximilian Philipp.
Tottenham had also been credited with an interest in Toljan, who was available at a cut-price fee having entered the final year of his contract at Hoffenheim, as a potential replacement for Kyle Walker. German publication Bild report that the player also had offers from both Spurs and reigning Serie A champions Juventus, but eventually opted for Dortmund as he sets his sights on earning a place in Joachim Low's senior Germany set-up.
Mauricio Pochettino appears to have identified Serge Aurier as the new right-back competition for Kieran Trippier and could find out later on Wednesday if the controversial Ivorian will be granted a UK work permit to complete his £23m move from Paris Saint-Germain.
Argentina Under-20 centre-back Juan Foyth's arrival from Estudiantes is also imminent, while moves for injured Everton playmaker Ross Barkley and out-of-favour Liverpool striker Divock Origi may also come to fruition before Thursday evening's transfer deadline. However, Tottenham will not be signing rumoured forward target Keita Balde Diao after AS Monaco confirmed the arrival of the Senegalese on a five-year contract.
Spurs have made just the two signings so far this summer, with defender Davinson Sanchez joining from Ajax in a club-record £42m deal and third-string goalkeeper Paulo Gazzaniga reuniting with compatriot and former Southampton manager Pochettino in north London.