He performed in the theatrical companies of Sir Frank Benson, Lillie Langtry, and Ellen Terry.
Lang and his wife subsequently formed their own company, which toured India, South Africa, and Australia from 1910 to 1913 performing Shakespeare.
He reprised this part in a 1919 silent film, and became so identified with the role that he titled his 1940 memoirs Mr. Wu Looks Back.
In 1916, Lang became one of the first major theatre stars to act on film, as Shylock in The Merchant of Venice, with his wife as Portia.
Lang also wrote the plays Carnival (1919) and The Purple Mask (1920), both of which were produced on Broadway and made into films.