Walker was born in Boston, Massachusetts. In 1879, he went Paris, France to study painting under Léon Bonnat at the École des Beaux-Arts. After returning to the United States in 1882, he lived for a few years in Boston, then moved to New York and set up a studio there. In 1884, Walker exhibited two portraits at the Boston Art Club, and in 1885 he exhibited another portrait.
In 1888, at the suggestion of Thomas Dewing, he established a studio in Cornish, New Hampshire. In Cornish he was part of the "Cornish Arts Colony" that included such artists as Dewing, Augustus Saint-Gaudens, Maxfield Parrish, Louis St. Gaudens, Charles A. Platt, and Kenyon Cox.
In 1888 he married Laura Marquand, a textile designer and decorative artist. He became a member of the National Academy of Design, New York, in 1902. Walker died in Belmont, Massachusetts.