The Belgian, who was signed by the Blues in January 2012, spent last season on loan at the German side where he impressed scoring 10 goals in 33 games.
De Bruyne's performances for die Werderaner earned him a place in the Belgium national team, and the 22-year-old has hailed his time in Germany as a fantastic learning curve.
|2/1||Chelsea are 2/1 with William Hill to win the Premier League
“I think I managed to have a good year and managed not to have my own injuries, so I was very happy.
“The Bundesliga is a strong competition. You can compare it to the Premier League, which is probably more physical, it's a lot of running, but every team tries to play good football and always goes for the win.”
De Bruyne followed Chelsea's performances last season closely and, having returned to Stamford Bridge, is looking forward to showing what he can do in a blue shirt.
“I managed to see the results, and some games, but not many because my own schedule was full,” the former Genk winger added.
“I spoke to people from the club regularly, and they came to watch games in Bremen, while I also talked to Eden Hazard in the national team also.
“It feels great to be back here now. I drove back from Belgium with Romelu Lukaku, through the channel tunnel. It's not that far and we enjoyed the trip.
“I had a good vacation after the season and in the end I was looking forward to starting again to get back to the normal life we are used to as footballers.”