[2] Hadorn was born in the family of farmers in Forst in Bernese Oberland.

He began to conduct research in his basement on amphibia and with Baltzer's encouragement he applied for a Rockefeller fellowship and went to University of Rochester[3] and met Curt Sturn and began to work with Drosophila.

One of his experiments was on the mutant Drosophila that had larvae that did not turn into pupae due to a defective hormone function.

In 1955 he published Developmental Genetics and Lethal Factors which was translated to English in 1961.

His other major work was on imaginal discs begun in 1945 and he worked out the fate of different regions producing "fate maps" using experiments with transplanting tissues and studying transdetermination.