The 20-year-old will wear the number 28 shirt during his time at the Signal Iduna Park.
Anselmino's move comes as Dortmund grapple with a defensive injury crisis, with key players Emre Can, Nico Schlotterbeck, and Niklas Sule all sidelined. Dortmund CEO Lars Ricken highlighted the urgency behind the signing.
"Due to the injuries in central defence, we've been forced to make adjustments. Aaron already has first-league experience in his home country and shows tremendous potential. There's a reason Chelsea handed him a long-term contract last summer," said Ricken.
Anselmino, who rose through the ranks at Boca Juniors, made his professional debut in 2023 and went on to make 18 appearances for the Argentine giants, scoring two goals and providing three assists. His standout performances prompted Chelsea to spend 15.6 million pounds to secure his signature in August 2024. After initially returning to Boca on a six-month loan, he joined Chelsea in January 2025.
While his game time in London has been limited, Anselmino made his Chelsea debut in the FIFA Club World Cup round of 16 against Benfica, helping the Blues in their successful campaign to lift the trophy. However, with competition for places under new manager Enzo Maresca, the decision was made to send the youngster out on loan for regular playing time.
Speaking about his move to the Bundesliga, Anselmino expressed enthusiasm for the new challenge.
"I'm really excited about Borussia Dortmund and will give my all for success with this great club and its great fans," said the youngster.
The Argentine becomes Dortmund's fourth major arrival of the summer window, following Jobe Bellingham from Sunderland, goalkeeper Patrick Drewes from Bochum, and the return of Carney Chukwuemeka from Chelsea on a permanent deal.
Anselmino could make his debut as early as this weekend, when Dortmund host Union Berlin in their second Bundesliga fixture following a 3-3 draw at St. Pauli on Matchday 1.
Meanwhile, Chelsea's international loan slots are nearing capacity. With Anselmino's move, the club has now used five of the six allowed international loan positions. The Blues continue to explore transfer options for players such as Nicolas Jackson, Christopher Nkunku, Tyrique George, Raheem Sterling, Ben Chilwell, Axel Disasi, David Datro Fofana, and Alfie Gilchrist, with further moves expected ahead of next week's transfer deadline.
Anthony Gordon has issued a public apology to his Newcastle teammates, fans, and Liverpool captain Virgil van Dijk following his red card in the dramatic 3-2 loss to the Reds at St James' Park on Monday.
Newcastle have had a 50 million pound bid for Wolves striker Jorgen Strand Larsen rejected, as they continue their urgent search for a new centre-forward before the transfer window closes on September 1.
Borussia Dortmund have completed the permanent signing of Chelsea midfielder Carney Chukwuemeka on a five-year deal running until June 2030.
Borussia Dortmund have officially extended head coach Niko Kovac's contract by one year, keeping him at the club until June 2027.
