Painter, printmaker, and illustrator Hans Nicolaj Hansen was born in Copenhagen, Denmark on May 15, 1853, the son of wine merchant C.J.A. Hansen and Sophie Andrup Hansen. After graduating in 1872 from the Borgerdyd Skolen Christianshavn he went on to attend the Royal Danish Academy of Fine Arts, graduating in 1877. That same year he exhibited for the first time at the famous Charlottenborg hall, earning a medal for an historical painting. He then performed his compulsory military service in the Faore Islands and in Iceland, later illustrating his experiences on the ship "Fylla". The following year he exhibited his first historical painting, “Outside Sigbrit Port”, one of many in the genre he would become known for. Later that year he went to Paris and trained further under painter Léon Bonnat.

Hansen married Ida Theodora Frederikke Rasmussen in the fall of 1883 and they traveled throughout Europe, settling for a time in Rome. After returning to Copenhagen in 1884 Hans set up a formal studio and went to work. He painted two oils that would raise his reputation among his peers and in the Copenhagen art world: a full portrait of his wife, sometimes called "The Figure of the Lady" (1885) and "The Sick at St. Helenæ Tomb Hoping to be Cured" (1887). From 1890 to 1891 he returned briefly to Paris to study with Puvis de Chavannes.

The Hansens built a summer residence and studio in Ørnebjerg, Rebild Bakker, in 1902, to which they added the "house mark" of a bird known as the Hjejle - a name his son Berndt and other descendants would take on as their surnames later in life. After a divorce around 1908, Hans married Ella Ruben daughter of Bernhard Ruben and Ida Susanne Ruben. They moved to a country house, called Christinelund, in Præstø. One of Hans' most famous works is the reworking of the painting from 1921, ”Christian X Riding Across the Frontier”, which hangs at the Museum of National History at Frederiksborg Castle.

Hansen was a member of the Academy Plenary, 1910 (Årsmedaljerne 1903 and 1910 for his etchings) and of The Academy in 1915. In 1909 he was elected chairman of the Graphic Artists Society, and in 1916 he became a Knight of the Dannebrog. He was given a retrospective of his works at Charlottenborg in 1913. Hans Nicolaj Hansen’s greatest reputation was as an illustrator and etcher, and he was frequently commissioned by publishing companies to illustrate books of historical nature or of fantasy. Among his most noted etching series was "Childhood Memories", a portfolio of remembrances from his earliest days.

Hans Nicolaj Hansen died on March 14, 1923 at Frederiksberg, Denmark.