Henry Sandham was born in Montreal in 1842. His father was a house painter by trade in the Griffintown neighbourhood of Montreal. Henry began to show great interest in art at an early age. By 1856, he had begun working in William Notman’s photography studio and by 1860, he was the assistant to William Notman’s partner, John Arthur Fraser, head of the studio art department. As there was no art school in Montreal at that time, Sandham acquired his training in drawing, watercolours and oil painting while on the job. He later developed his skill in human figure drawing by studying anatomy with a physician.
When Fraser left in 1868 to open the Toronto branch of Notman & Fraser, Sandham took his place as head of the art department. During the 1870s, he refined the technique of producing large composite photographs that the Notman studio are widely known for. Sandham was awarded a silver medal at the 1878 Exposition Universelle in Paris for a large scale, three-hundred-person group photo of the McGill Snow Shoe Club. He became partners with Notman in 1877 and the studio was renamed Notman & Sandham. This partnership lasted until 1882.
Sandham began creating illustrations for Scribner’s Monthly in 1877. The illustrations and series-drawings that he created over this three year period eventually led to be named a charter member of the Royal Canadian Academy of Arts.
Sandham and his wife, Agnes Fraser, toured England and France in 1880. At the end of that year they also visited Boston, Massachusetts, on account of some portrait commissions. They enjoyed their visit so much so that they decided to stay for nearly twenty years. It was during this time that Sandham focused primarily on his art and less on business. He produced portraits, historical paintings and illustrations. His work was exhibited regularly at the Boston Art Club, American Watercolor Society of New York as well as at the World's Columbian Exposition, 1893, Cotton States and International Exposition, 1895, and Tennessee Centennial and International Exposition, 1897.
Sandham moved to London, England in 1901 to further his career. His work was exhibited at the Royal Academy of Arts from 1905 to 1908. Agnes Fraser died in 1906, and Sandham in 1910. He is buried in Kensal Green Cemetery in London.