He studied chemistry and biochemistry at Imperial College, University of London (earning a B.Sc.

After several years teaching at the University of London, Thimann moved to the California Institute of Technology in 1930.

[1] Thimann moved to University of California, Santa Cruz (UCSC) in 1965—the year of its founding—to become the first provost of Crown College.

He also played a central role in fostering the UCSC Arboretum and its botanical collection.

After retiring as provost in 1972, Thimann remained at UCSC until 1989, when he moved to Haverford, Pennsylvania.