She pursued her theatrical education at the Royal Academy of Dramatic Art (RADA) in London, where she was the first American to receive the school's silver medal.

She later performed in 14 Broadway productions, including The Passion of Josef D., The Physicists (for which she received the 1965 Clarence Derwent Award for Most Promising Female), A Time for Singing, A Day in the Death of Joe Egg, I Remember Mama and Dance a Little Closer.

[citation needed] Hubbard's pairing with the character of Dr. Nick Bellini (Gerald Gordon) made them one of the most popular romantic couples in soap operas, dominating the show's storyline during the later half of the 1960s and for most of the 1970s.

In 1970, Hubbard made her big screen debut in the Academy Award-nominated drama film I Never Sang for My Father opposite Melvyn Douglas and Gene Hackman.

[citation needed] She also appeared in films The Bell Jar (1979), Ordinary People (1980), Cold River (1982), Center Stage (2000), and The Treatment (2006).

After The Doctors was cancelled, Hubbard joined the cast of One Life to Live in the recurring role of society matron Estelle Chadwick.

[citation needed] Hubbard left the program in 1999 due to a disagreement over the character's direction, but was persuaded to return several months later by the show's new executive producer.