Teller worked as a postdoctoral researcher at the University of Göttingen, a leading center for theoretical physics at the time. However, the rise of the Nazi party led to dismissal of Jewish academics and he was looking for positions elsewhere.

With the rise of Nazism in Germany, Teller, concerned about his safety due to his Jewish heritage, emigrated from Europe. He was aided by the International Rescue Committee.

Teller worked with Niels Bohr in Copenhagen for a year, a key experience influencing his later work.

Teller secured a position as a professor of physics at George Washington University in Washington, D.C. He collaborated with George Gamow on nuclear physics and beta decay. He also met his lifelong friend Leo Szilard in 1939.

Teller played a role in conveying Leo Szilard's concerns about nuclear fission to Albert Einstein, leading to the Einstein-Szilard letter to President Franklin D. Roosevelt. This letter was instrumental in initiating the U.S. research into atomic weapons.