Nicolai Hammer was born in Copenhagen, Denmark on July 16, 1887.  He studied art at the Academy there between 1907 and 08. Hammer traveled extensively, studying at the Academy in Dresden, Germany between 1909 and 1910. He then traveled to Holland, Belgium and England in 1924. While living in England he studied printmaking with W.P. Robins. He taught printmaking at the Art Academy in Copenhagen with Axel Jorgensen. Hammer returned to London and Paris in 1929, Germany in 1935, Paris and Holland in 1936 and Venice in 1951 and 1954.

Hammer is known mostly as an etcher, his images drawing heavily on his travels and on the Danish architecture, many printed in color. The British influence of Robins and Whistler is evident in the composition of many of his early works. Hammer exhibited extensively throughout Scandinavia and Europe.

Nicolai Hammer died in Copenhagen on November 4, 1970.