As a child, Juliet Mills appeared as an extra in various films, including a role as Freda’s 11-week-old baby in the 1942 film In Which We Serve, starring her father. Her first major role came in 1958, when she was 16, as Pamela Harrington in the Peter Shaffer play Five Finger Exercise. The show ran one year in London, and then moved to the Music Box Theatre on Broadway. In 1960, Mills was nominated for a Tony Award as “Best Featured Actress” for her performance as Pamela.
Her role as a stowaway dressed as a man, but daughter of a ship’s gunner, in episode 2 of Sir Francis Drake was one of her first TV appearances (1961) and was echoed by an almost identical role in the 1964 film Carry On Jack.
In the 1960s, she would act both in films and on television, including the film, The Rare Breed with James Stewart and Maureen O’Hara, and on television series such as The Man from U.N.C.L.E., Ben Casey and 12 O’Clock High. The 1970s saw her working mostly in television, although she has stated that the highlight of her film career was the film Avanti! (1972), directed by Billy Wilder, in which she starred with Jack Lemmon and for which she received a Golden Globe Award nomination in 1973.
In 1974 Mills starred alongside fellow English actor Richard Johnson in the Italian horror film Beyond the Door, playing the role of Jessica Barrett, a woman who becomes demonically possessed after an unplanned pregnancy. Mills also appeared in a two-part 1978 episode of the TV series The Love Boat, playing Barbara Danver, wife of Alan Danver, played by Dan Rowan, one half of the comedy duo Rowan & Martin.
She is perhaps best known for starring on the American television series Nanny and the Professor, which was called an American version of Mary Poppins. She was again nominated for a Golden Globe Award in 1971 for the same role. Despite strong ratings, the series ran only two seasons, in 1970 and 1971.
In 1974, she won an Emmy Award for “Outstanding Single Performance by a Supporting Actress in a Comedy or Drama Special” for her performance in the miniseries adaptation of QB VII. During the 1974–75 television season, she also had a recurring role as Dr. Claire Hanley on NBC’s Born Free. In 1980, Mills returned to the stage, starring in The Elephant Man, with Maxwell Caulfield. The two actors hit it off, and the younger Caulfield became her third husband, leading Mills to withdraw from acting for a time.
In 1999, she was cast on the daytime drama Passions as Tabitha Lenox, a witch who was burned at the stake in the 17th century. Initially, the character wished harm on other people, but in a June 2007 episode, the character was declared a “good witch”. Mills was nominated for her first Daytime Emmy Award for “Outstanding Lead Actress” for the role.
The series ended in August 2008. In 2009, Mills joined the cast the ITV drama Wild at Heart, playing Georgina, the sister of a character played in the previous series by her real-life sister Hayley. She also guest-starred in two episodes of Hot in Cleveland as Philipa Scroggs, the mother of Joy (played by Jane Leeves).