The young defender has been in outstanding form in the 2010-11 campaign and his good performances haven't gone unnoticed in Spain
The Catalan powerhouse have had to employ midfielders Sergio Busquets and Javier Mascherano at the back in recent weeks due to a lack of cover and are eager to add some depth to their back line.
Hummels has developed into a key player at Dortmund since joining them from Bayern Munich in January 2008 and the 22-year-old is considered to be one of the best young defenders around in Europe.
Barca face stiff competition from Inter in the race for Hummels' signature, while the stopper has also been linked with a move to the Premier League.
Nevertheless, Hummels won't be available on the cheap as he recently signed a contract extension at the German champions until the summer of 2014.