Jensen was the son-in-law of the journalist and writer Johann August Moritz Bruehl (1819–1877), the father-in-law of the historian and editor Eduard Heyck, botanist Carl Christian Mez and Ernst, Prince of Saxe-Meiningen, the grandfather of the writer and poet Hans Heyck and the step grandfather to psychologist Narziß Ach.

He, however, abandoned the medical profession for that of writing, and after engaging for some years in individual private study proceeded to Munich, where he associated with men of letters.

After a residence in Stuttgart (1865–1869), where for a short time he conducted the Schwabische Volkszeitung and became the lifelong friend of the writer Wilhelm Raabe, he became editor in Flensburg of the Norddeutsche Zeitung.

In 1872 he again returned to Kiel, lived from 1876 to 1888 in Freiburg im Breisgau, and from 1888 until his death was a resident of Munich and St. Salvator near Prien on Lake Chiemsee.

[1] Jensen was a prolific German writer of fiction, publishing more than one hundred and fifty works, but only comparatively few of them became popular, such as the novels, Karin von Schweden (Berlin, 1878); Die braune Erica (Berlin, 1868); and the tale, Die Pfeifer von Dusenbach, Eine Geschichte aus dem Elsass (1884).