Born as Marinus Rasmussen, he changed his name in 1910 to Marinus Børup. He graduated from Aarhus Cathedral School in 1910. In World War I he joined the army and rose to the rank of Lieutenant. He later worked as a teacher at several schools, but also wrote prodigiously, including work for newspapers from 1934-46 as a theatre and book reviewer. He published his first poetry in 1916 with a collection of poems, followed by several other series: Dugg (1918), Nakjælen (1919), Gækkeliljer (1920), Drillerier (1920), Kimblade (1921), Den hilsende Klinge (1921), Tøbrud (1923), Regnbuen (1927), Maj. Kærlighedsdigte (1947), and Nattevagten og andre Dyrebilleder (1949), which generally continues the tender tradition of the 19th century. His main work was Steno, hans Livs Historie (1938), a mixture of drama, poetry and and narrative, a masterpiece of the time poetry. Vorlad os vor Skyld (1928) is a development and marriage novel. He has also newly translated comedies by Molière as well as French poetry and gospels from Greek.