In 1858 he applied to the Grand Duchy of Baden for a position in diplomacy without salary. He initially served at the legation of the Grand Duchy of Baden at the Prussian court in Berlin. In 1861 he was transferred to Paris as secretary of the legation and given a salary. In 1862 he was transferred to the Delegation in The Hague. Bohlen-Halbach was promoted to envoy extraordinary and minister plenipotentiary in The Hague in 1866[3] and ennobled on August 14, 1871, adding von to his name. After the embassy was dissolved, he moved to Karlsruhe in 1878.[2] There he became court ceremonial master in 1881.[2]
On December 29, 1862, Bohlen-Halbach, married Sophie (née Bohlen; 1837–1915), at Velsen, Netherlands. She was a daughter of Henry Bohlen, who served as a general in the Union Army and died only months before the wedding in the American Civil War. Her father was a half-brother of Gustav's mother which ultimately made them half-first cousins. They had nine children together;
- Arno Heinrich Halbach (1863–1896)
- Alwyn Gustav von Bohlen und Halbach (1865–1938)
- Harry Carlo von Bohlen und Halbach (1866–1919)
- Fritz Petil Borin von Bohlen und Halbach (1868–1941)
- Gustav Krupp von Bohlen und Halbach (1870–1950) whom married Bertha Krupp
- Carolina Emily Sophie Ernestine von Bohlen und Halbach (born 1872)
- Emily von Bohlen und Halbach (1874–1939)
- Wilhelm Friedrich Hans von Bohlen und Halbach (born 1878)
- Kurt von Bohlen und Halbach
On October 14, 1871, Bohlen-Halbach, was ennobled and therefore added the von to his name, this also applied to his descendants. In 1878, he moved from The Hague to Karlsruhe, where in October 1885 he purchased Obergrombach Castle near Bruchsal. He died aged 59 in Karlsruhe in 1890 and was buried at Obergrombach.
In Obergrombach (Bruchsal) there are two streets named for the couple; Gustav-von-Bohlen-Straße and Sofienstraße.
Kösener Corpslisten 1930, 69, 488 (in German)
Manfred Koch: Die badischen Wurzeln der Krupp-Dynastie, in: Blick in die Geschichte Nr. 103, 27. June 2014 (in German)
Bringmann, Tobias C. (2001). Handbuch der Diplomatie, 1815–1963: Auswärtige Missionschefs in Deutschland und Deutsche Missionschefs im Ausland von Metternich bis Adenauer (in German). Berlin: Walter de Gruyter.