Jendrassik completed his education at Budapest's József Technical University, then at the University of Berlin attended lectures of the famous physicists Einstein and Planck. In 1922 he obtained his diploma in mechanical engineering in Budapest. From 1927 he worked at Ganz Rt, where he helped to develop diesel engines. He designed the world famous Jendrassik Cs-1 turboprop engine, of which the first few pieces were made with single and double cylinders; later, the 4- and 6-cylinder four-stroke versions were developed, without compression and with mixing chamber.The world's first turboprop was the Jendrassik Cs-1, designed by the Hungarian mechanical engineer György Jendrassik. It was produced and tested in the Ganz factory in Budapest between 1939 and 1942. It was planned to fit to the Varga RMI-1 X/H twin-engined reconnaissance bomber in 1940, but the program was cancelled.
Later on he was active in improving gas turbines and in order to speed up research, he established the Invention Development and Marketing Co. Ltd. in 1936. His reputation continued to grow, and he became the factory's managing director from 1942 to 1945. In recognition of his scientific work he was elected in 1943 corresponding member of the Hungarian Academy of Sciences. After the war he was not able to continue developing gas turbines. Political distrust surrounded him, and therefore he did not return from one of his travels abroad. He lived in Argentina for a while, then settled in England, where he established his own workshop, becoming in addition a consultant to the Power Jets company. The number of his inventions on record in Hungary is 77. His last invention of great importance was the pressure-compensating device.