Edmund Osthaus was born in Hildesheim, Hannover (now part of Germany), on August 5, 1858. He studied in Düsseldorf, Germany, with Andreas Muller, Peter Jansen, E. von Gebhardt, Ernst Deger, and Christian Kroner. In the early 1860s Osthaus' parents and younger siblings moved to Mexico in the employ of the Austrian Archduke Maximilian, whom Napoleon III had installed as Emperor of Mexico while the United States was distracted from foreign affairs by the Civil War; when his rule there was overthrown the Osthauses moved to Oshkosh, WI. Edmund joined them in 1883. Shortly afterward he moved to Toledo, OH, at the invitation of David R. Locke, a local newspaperman and collector. He became chief instructor at the Toledo Academy of Fine Arts and served as its director from 1886 to 1893. An avid upland game and waterfowl shooter and gun dog enthusiast, Osthaus specialized in portraits of setters and pointers; he painted many champion dogs from the 1880s to the 1920s, and was a founder of the National Field Trial Association in the 1890s. As well as commissioned portraits, he produced a series of postcards, prints and calendar pictures for duPont. He lived in Toledo for much of his life; after 1911 he also had a house and studio in Los Angeles, CA, as well as a house in Summit, NJ.

Osthaus was a member of the Tile Club in Toledo; he exhibited there regularly, showing such works as his Partridge Shooting and Retriever, both in 1903. At the Art Institute of Chicago (IL) he showed Still Evening in 1903 and, in 1911, Early Rambles and Setters. The Port Huron, MI, Museum of Arts and History has his Major, a portrait of a St. Bernard, and In the Field. The Toledo Museum of Art has another portrait of Major, among other works. The Butler Institute of American Art in Youngstown, OH, has his Family Portrait and his Setters in a Field is at the Morris Museum of Arts and Sciences in Bernardsville, NJ.

Osthaus died at his hunting lodge in Marianna, FL, on January 30, 1928.