Daniels began her stage career at the age of four, in a production of Shakespeare's Richard III. She was soon making films. Her career shifted to the United States; the 1910 Wizard of Oz was her second American movie, and was followed by 200 more. She was a major star in musicals, most famously in 42nd Street (1933).
After her 1930 marriage to Ben Lyons, her orientation turned back toward England. Her American film career languished in the later 1930s, though she became a major star on the London stage, and a prominent radio personality along with her husband.