The daughter of a Scottish-born father who managed a touring theatrical company starring her Spanish-born mother, she was appearing regularly in plays by the time she reached four. At nine she made her screen debut in the Selig company two-reeler THE COMMON ENEMY (1910), then played other child parts in numerous other shorts, mostly Westerns and adventure pictures, while attending a Los Angeles convent. At 14 she began playing adult roles in two-reel Hal Roach comedies, starring Snub Pollard and Harold Lloyd. From 1914 to 1918 she was featured in some 200 of these shorts, including most of the LONESOME LUKE and THE WINCKLE series with Lloyd.

In 1919, Miss Daniels signed a long-term contract with Paramount. She subsequently starred in several De Mille films and many other Paramount features through the rest of the silent era. Typically, she played light leads, impish, warm, often comic. But occasionally she portrayed hardened, experienced playgirls and a variety of other roles. Next to Gloria Swanson and Pola Negri, Miss Daniels was the most popular Paramount star of the silent period. Among her leading men were Wallace Reid and Rudolph Valentino. With the advent of the talkies, she was dropped by Paramount and signed up with RKO where, in the popular 1929 production RIO RITA  , she proved she could not only talk but also sing. In 1930 she married Ben Lyon, her co-star in ALIAS FRENCH GERTIE   and several subsequent films.

By the mid-30s' the Hollywood careers of both Lyon and Daniels were on a decline, and in 1936 the couple accepted an offer to appear in the London Palladium. They remained in London through WWII, appearing in music halls, on stage, and in a long-running radio show on BBC, and entertaining US troops. In 1946 they returned to Hollywood, where Lyon took an executive position with Fox, then, in 1949, went back to England, where the couple headlined another popular 50s family radio show "Life with the Lyons." They also made two mediocre films based on the series. Miss Daniels, who never gave up her American citizenship, suffered a number of strokes in the early 60s and finally succumbed to a cerebral hemorrhage.