Blyth was born in London. In 1841 he travelled to India to become the curator of the museum of the Royal Asiatic Society of Bengal. He set about updating the museum's catalogues, publishing a Catalogue of the Birds of the Asiatic Society in 1849. He was prevented from doing much fieldwork himself, but received and described bird specimens from Hume, Tickell, Swinhoe and others. He remained as curator until 1862, when ill health forced his return to England. His The Natural History of the Cranes was published in 1881.
Species bearing his name include Blyth's Reed Warbler and Blyth's Pipit.