James Fletcher was born on March 28, 1852, in Ash, near Rochester, Kent, England.

He was a Canadian entomologist, botanist, and writer. He began work as a clerk at the Bank of British North America in London and was transferred to the Montreal branch in 1874 and the Ottawa branch in 1875. In 1876, he began work as an assistant in the Library of Parliament and discovered an interest in botany and entomology. He established a national reporting system to help identify and control the spread of insects and weeds harmful to agriculture. In 1887, he became the first Dominion Entomologist and Botanist attached to the Central Experimental Farm. He helped set up measures to control the spread of plant diseases and harmful insects from both within and outside Canada. He was a founder of the American Association of Economic Entomologists, now the Entomological Society of America, and a fellow of the Linnean Society of London. He was one of the founding members of the Ottawa Field-Naturalists' Club and a president of the Ottawa Horticultural Society. In 1885, he was elected to the Royal Society of Canada. He contributed articles to scientific journals and bulletins, and he published with George H. Clark, “The Farm Weeds of Canada” (1906).

In 1879, he married Eleanor Gertrude Schreiber (1859–1912). He died on November 8, 1908, in Montreal, Quebec.