He studied at the Royal Danish Academy of Fine Arts from 1868 to 1875, specializing in figure painting, but did not pass the graduation examination.

[2] Nevertheless, Johansen is remembered particularly for the subdued lighting effects of his interiors — many of which were painted after his visit to Paris — as in his Glade jul (Merry Christmas, 1891),[note 1] Aftenpassiar (Evening Talk, 1886) and Aftenselskab i kunstnerens hjem (Evening Gathering at the Artist's Home, 1899) and his scenes of domestic family life, but he also painted landscapes (at Skagen, at Tisvilde, and at his childhood home, the fishing port of Dragør outside Copenhagen), still lifes and portraits.

[4] It is said that in Skagen, he showed just as much interest in playing Mozart on the hotel piano or Gluck on the church organ as in painting.

Martha often served as a model, for example in Køkkeninteriør (Kitchen interior, 1884) — which may have been inspired by Anna Ancher's similarly composed The Girl in the Kitchen — Sovekammerscene (Bedroom Scene, 1885) and Børnene vaskes (Washing the Children, 1888) which were painted partially on the basis of photographs.

In 1889, many of the Skagen artists received awards at Exposition Universelle in Paris; Johansen won a Gold Medal for Børnene vaskes.