Constantine d'Ohsson came to Sweden in 1798, and graduated from the Uppsala University in 1799. That same year he became clerk at the Foreign office and spent 1801–03 as an attaché in Paris, where he occupied himself with researches in Oriental history. He was a legation secretary in Madrid in 1805–06, at the embassy of the Prussian royal court in 1807–08, in Seville (where the Spanish insurrectionary government had its headquarters) in part of 1809, and in Paris, where he served as charge d'affaires from 1811 to 1813. Later he served a term as Cabinet Secretary to Crown Prince Karl Johan, was appointed in 1816 to the Swedish Minister at The Hague, was moved in the same capacity to Berlin in 1834 and recalled from there in 1850.