The Argentina U-20 center back joins Dortmund's core of rising teenage stars.
Borussia Dortmund have announced the signing of teenage defender Leonardo Balerdi after capturing the Argentina Under-20 center back from Buenos Aires giants Boca Juniors.
Balerdi has signed a 'very long-term' contract with Dortmund and began training with his new teammates within hours of putting pen to paper.
He has already been assigned the club's vacant No. 18 shirt, last worn by Sebastian Rode prior to his loan exit to Eintracht Frankfurt earlier this month.
Dortmund sporting director Michael Zorc confirmed that the transfer had originally been planned for the coming summer, but was brought forward to January.
"Leonardo is an intelligent centre-back and strong in defence," Zorc added.
"He also has a good build-up and passing game. We are very glad that he has chosen us and are convinced that he will help us with his talent in the future."
Balerdi, who has played just a handful of first team games in his career to date after making his debut with Boca last year, sees a continuation of Dortmund signing emerging talents after landing the likes of Jadon Sancho, Alexander Isak, Dan-Axel Zagadou in recent seasons.
Dortmund are currently on course to win a first Bundesliga title since 2012. At the halfway stage of the season Die Schwarzgelben have won 13 of their 17 games, losing just once, and lead reigning champions Bayern Munich by a handsome six point margin.