William trained with his Great-Uncle Thomas Sidney Cooper at his School of Art in Canterbury. William became a successful artist exhibiting at the Royal Academy, the Royal Society of British Artists (Suffolk Street galleries, London) and the Royal Watercolour Society.
Cooper married in 1882, and in 1890 moved to Herne Bay in Kent where he remained for the rest of his life. As well as painting professionally, he was a keen golfer and liked to play Tennis and Bowls. He was also a musician and took part in local musical events. He built many houses in and around Canterbury, the best known being, Alcroft Grange.