Featherston Osler was born on January 4, 1838, in Newmarket, Upper Canada, the son of Rev. Featherstone Lake Osler (1805–1895) and Ellen Free Pickton (1806-1907), and brother of Sir Edmund Boyd Osler (1845–1924), M.P. and Dr. William Osler (1849–1919).,

He was a barrister. He was educated at local schools in Bond Head and Barrie, Ontario. He served in the law firm of James Patton in Toronto and was called to the bar in 1860. He was made a puisne judge of the Court of Common Pleas in 1879. In 1883, he was appointed Chief Justice of the Court of Appeal in Ontario. He retired from the Bench in 1910 and became president of the Toronto General Trusts Corporation. From 1921 to 1924, he served as a Treasurer of the Law Society of Ontario. In 1861, he married Emma Henrietta Smith (1839–1902). He died on January 16, 1924, in Toronto, Ontario.