In 1815, Walker went to London to study as a stipple engraver under Thomas Woolnoth.
[4] He established his reputation by engraving a large plate of Sir Henry Raeburn's equestrian portrait of John Hope, 4th Earl of Hopetoun.
In 1829, on his marriage to Elizabeth Reynolds, the famous miniaturist, he settled at 64 Margaret Street, where he resided until his death.
Walker's work consists of about one hundred portraits of eminent contemporaries, after various oil painters, chiefly in mezzotint, all published by himself.
Whilst being principally remembered as an engraver, Walker was also an able sculptor, his notable work being the figure of Queen Elizabeth I on the Scott Monument on Princes Street in Edinburgh.