In 1946 he defended his doctoral thesis in Nordic languages titled "Studier över de svenska ortnamnen på -inge" (studies on Swedish place names with -inge).

He worked at the Royal Swedish Academy of Letters, History and Antiquities between 1946 and 1954.

He was, however, forced to leave the position in 1971 due to declining health, but began working as a researcher at the Swedish Academy.

He was president of Svenska språknämnden, a predecessor of the current Swedish Language Council, from 1967.

Ståhle was also president of Svenska Vitterhetssamfundet (The Swedish Society for Belles-Lettres) from 1969 until his death.