In 2001, he was appointed lecturer at Imperial College London. He has written one book entitled Mutants: On the Form, Varieties and Errors of Human Body for which he was awarded the Guardian First Book Award in 2004. In 2004 he adapted his book into a television documentary series for Britain' Channel 4 entitled Human Mutants.
Leroi has presented two other TV documentary series for Channel 4: "Alien Worlds" in 2005 and "What makes us Human" in 2006. Despite his TV appearances, Leroi expressed scepticism of the motivations of television creatives in an email exchange with director Martin Durkin in which he said "left to their own devices, TV producers simply cannot be trusted to tell the truth".http://ocean.mit.edu/~cwunsch/papersonline/durkinemails.htm
He is also known as one of the first testers of the beneficial acclimation hypothesis. In 2005, Leroi published an article in the New York Times entitled "A Family Tree in Every Gene", which argued for the usefulness of racial types in medical genetics.