This museum, established in 1945, is the successor to the Folkwang Museum founded in 1902 in Hagen by Karl Ernst Osthaus and is seen today as being part of the so-called "Hagen Impulse" tradition. The collection of classical modern art reflects this historical aspect. In addition there are equally important architectural examples of the Hagen Impulse. Further, the collection and exhibition activities at the Osthaus Museum have been further enhanced by its collection of specific pieces of international contemporary art. This is true to Osthaus’ central philosophy concerning the exploration of contemporary art.

Since it was reopened in August 2009, the renovated and expanded Osthaus Museum Hagen has displayed its collection in the historical Folkwang building: Late impressionist pieces and expressionist and classic modernism pieces can be seen in the entrance hall around the “Minne-Fountain” and in the sky-lit rooms on the top floor. There is also a room with works by Christian Rohlfs. The “Architecture of Memory” by Sigrid Sigurdsson tackles the consciousness of history. The newly established "Young Museum" educational collection housed in the historic basement offers a varied educational program, which takes into account current demographical developments as well as intercultural dialogue. 

In accordance with Osthaus’ philosophy, special exhibitions featuring modern and contemporary art make the meaning of art for society accessible by using different aspects to symbolise the ever-shifting understanding of art and its link to historical and contemporary social conditions.

Hohenhof, the former home of Karl Ernst Osthaus and his family in Hagen-Emst, is now a branch of the Osthaus Museum. Built by van der Velde, it is now an attraction on the "Industrial Heritage Trail" in the Ruhr region.