Born into a working-class family in Nakskov, he trained as a shipbuilder before hiring on as a ship's carpenter in 1872. He came to Bangkok for the first time in 1873 and advanced to first mate and later master of a ship owned by the king of Siam. Subsequently, he entered the freight business in East Asia and later Europe. In 1885 he started his own company, Andersen & Co., which encompassed import/export, shipping, logging and sawmills.
During World War I, in which Denmark remained neutral, he went on missions to several countries, attempting unsuccessfully to initiate peace negotiations, but more successfully to secure Danish interests.