He was born in Bergen as the youngest son of factory owner and ship-owner Peter Jebsen (1824–1892) and Sophie Catharina Sundt (1849–1912).
He took the doctorate in Zurich in 1905 with the thesis Zur Kenntnis der Phenoxymucobrom- und Chlorsäure als aromatische Verbindungen.
During the post-World War I economic crisis he had to leave Elektrokemisk in 1920, but became chief executive officer of Titan Co. in 1924.
The shares in Titan Co. plummeted until being bought in 1927 by the American corporation National Lead along with the patent rights for titanium white.
Jebsen was hired in National Lead, and worked out of Paris, from 1929 as chief executive of Titan Co. Inc in Europe.