Kathlyn Williams was born Kathleen Mabel Williams on May 31, 1879 in Butte, Montana, and the only child born to Joseph Edwin "Frank" Williams, a boarding house proprietor, and Mary C. Boe (1846–1908) of Welsh and Norwegian descent. Many biographies state her birth year as 1888; however, she is listed on the 1880 United States Census as being a year old. Williams displayed an early interest in becoming an actress in her youth which lead her to become a member of a community thespian group. She also joined the Woman's Relief Corps that allowed her to showcase her vocal prowess at local recitals.

Williams began her career with Selig Polyscope Company in Chicago, Illinois and made her first film in 1908 under the direction of Francis Boggs. By 1910, she was transferred to the company's Los Angeles film studio. Williams played "Cherry Malotte" in the first movie based upon Rex Beach's 1906 novel The Spoilers in 1914, a role portrayed in subsequent versions by Betty Compson (1930), Marlene Dietrich (1942), and Anne Baxter (1955). In 1916, she starred in the thirteen episode adventure film serial, The Adventures of Kathlyn. She was busy throughout the silent film era but age and the advent of talkies saw her make only five sound films, the last in 1935. Kathlyn evolved from a comedian and serial player in silents to portraying character roles in the early 1930s.