During the next year, he transferred to Leiden University, to study physics and mathematics, and he earned his bachelor's degree in 1920 (Dutch: Kandidaatsexamen).

While there, he attended lectures by Tullio Levi-Civita and Vito Volterra and met his longtime friend, Enrico Fermi.

Ehrenfest assigned him to work with his graduate student, Samuel Goudsmit for a quick update on "what was currently happening in physics".

During part of World War II, from 1943 through 1945, Uhlenbeck led a theory group at the Radiation Laboratory in Cambridge, Massachusetts, which was doing radar research.

[6] Uhlenbeck was a friend of many of the great physicists and mathematicians of his era, including Enrico Fermi and Oskar Klein.

He wisely observed that what is often of lasting value is not the first original contribution to a problem, but rather the final clearly and critically written survey.

He felt that something really original one did only once – like the electron-spin--the rest of one's time one spent on clarifying the basics.Cohen also comments on the high quality of Uhlenbeck's teaching: He was an inspiring teacher.

With superbly organised and extremely clear lectures, he laid bare for everyone to see the beautiful structure of statistical mechanics, based on the principles of the founding fathers, Maxwell, Boltzmann, and Gibbs.