He became a merchant's apprentice in his maternal uncle Arnold Philipsen's wholesale company on Store Købmagergade in 1858.

At the outbreak of the Second Schleswig War in 1864, he immediately enrolled as a volunteer and was severely wounded in the Battle of Lundby on 3 July.

[1] In September 1868, Petersen was granted a license as a merchant in Copenhagen and established a trading house under his own name in Nygade.

The factory was established as a separate company but was acquired by Holger Petersen's trading house after his death in 1917.

In July 1900, the company bought the plantations Castle Cockley, Pearl and Cassavagarden on Saint Croix.

In 1903, he was part of a delegation which traveled to the Danish West Indies and purchased a number of new plantations on the three islands.

In 1909, he was a driving force behind A/S Vestindisk sukkerfabrik's acquisition of Jacob Lachmann's sugar refinery on Saint Croix and was himself appointed as chairman of the board.

Oktober (Association of 5 October), a secret credit institution which contributed to keeping North Schlesvig land on Danish hands against the explicit policy of the Prussian government.

He was active in the Association for the Education of Young Merchants (Foreningen til unge handelsmænds uddannelse).

He established Holger Petersen's Foundation with an initial capital of DKK 7 million by testament of 2 December 1919.