Howard began his professional acting career in regional tours of "Peg O' My Heart" and "Charley's Aunt" in 1916–17 and on the London stage in 1917, but had his greatest theatrical success in the United States in Broadway theatre, in plays such as "Aren't We All?" (1923), "Outward Bound" (1924) and "The Green Hat" (1925). He became an undisputed Broadway star in "Her Cardboard Lover" (1927). After his success as time traveller Peter Standish in "Berkeley Square" (1929), Howard launched his Hollywood career in the film version of "Outward Bound", but didn't like the experience and vowed never to return to Hollywood. However, he did return, many times—later repeating the Standish role in the 1933 film version of "Berkeley Square".