Born on 17 July 1858 in Roskilde, Pauline Thomsen was the daughter of the lecturer Christen Thomsen (1822–1874) and Pauline Mathea Georgine Bergstrøm (1831–1896). From 1877 to 1880 Thomsen attended Vilhelm Kyhn's art school in Copenhagen as the Academy did not admit women until 1888. She adopted his Romantic approach in the landscapes she painted first in Zealand and later together with Kyhn's former students in the area around Ry and Himmelbjerget in Jutland. Her landscapes seldom include figures but often have striking groups of trees. Like Kyhn, she gave the sky and cloud formations an important place in her paintings. Her few portraits are mainly pen-and-ink or charcoal drawings. She exhibited at Charlottenborg Spring Exhibition from 1885 to 1931 but also exhibited at Kunstnernes Efterårsudstilling in 1905 and 1907. In 1895 she exhibited in Chicago and in 1900 in Paris at the World Exhibition.