Bremen had the game's first chance when Aaron Hunt made his way down the flank before finding Franco di Santo at the near post, but he was put off from making a shot by the Dortmund defence.
Marco Reus was first to threaten for the visitors when he latched onto a long ball from defender Sokratis Papastathopoulos. However, his attempt was blocked on its way to goal.
Dortmund made the best of a scrappy opening to take the lead in the 26th minute when lone frontman Robert Lewandowski drilled a clinical finish into the bottom corner of the goal.
Bremen had the chance to equalise before half time when Sebastian Prodl rose highest to meet a cross from Ludovic Obraniak, only to head disappointingly over the crossbar.
Henrikh Mkhitaryan then doubled Dortmund's lead going into the break when he crashed home an effort into the far corner of the goal, having beaten two Bremen defenders with an industrious run from midfield.