Leonard Mandel was born on 9 May 1927 in Berlin, Germany. Due to his Jewish background, his family emigrated to England and then to the USA. He earned his doctorate at the University of London. He worked at Imperial College London and then at the University of Rochester, where he spent most of his career. Together with Chun Ki Hong and Zheyu Ou in 1987, he experimentally observed the effect of two-photon interference. He was awarded the Max Born Award and other honors. He died on 9 February 2001.