Immaculate Heart High School was founded in 1906 by the Sisters of the Immaculate Heart of Mary, a Catholic religious order of women who trace their origin to Olot, Spain, where they were founded by Father Masmitja de Puig in 1848.

In 1903, under the auspices of Bishop Thomas J. Conaty, the sisters later purchased a fifteen-acre plot of land for $10,000 in the Hollywood Hills at what is now Western and Franklin Avenues. The property at that time was outside the city limits, flanked by olive and orange trees and approached only by a wagon road.

On April 24, 1905, the ground-breaking took place for a grayish-white, red roofed edifice of Moorish, mission architecture. This convent building included classrooms for high school and elementary school students, boarding facilities for the girls, and living quarters for the sisters.

In June 1906, six young women became the first graduates of the school which then had a total enrollment of 75 students. The curriculum developed to include Greek, Latin, French, Spanish, English, history, mathematics, physiology, chemistry, physics, music, art, and drama. In 1908, Immaculate Heart became the first private school in Southern California to receive college accreditation.

Immaculate Heart soon established its reputation as an excellent college preparatory school for young women. By far the majority of its more than 9,000 graduates continued their education at colleges and universities across the country. They have served with distinction as artists, musicians, educators, journalists, doctors, lawyers, engineers, scientists and stars of stage and screen, to name but a few of the many professions and careers they have entered. Immaculate Heart graduates were often pioneers in professions not accustomed to having women.

In 1946, a 24,000 square foot auditorium/classroom building was constructed. When the original convent building, after sustaining significant earthquake damage, was condemned by the City and torn down in 1973, it was replaced by a 24,000 square foot library/classroom building. Later additions to the campus included: the cafeteria building (1983); the small chapel, La Capilla de Maria (1987); the administration building and student/faculty center (1990) and the playing field (1992). In the summer of 1998, major renovation of the auditorium building included the remodeling of the visual arts facility which yielded two large classrooms for studio arts and a computer graphics lab. The auditorium itself was renovated to meet the needs of the performing arts and athletics programs. In June 2005, a new sports facility was completed adjacent to the swimming pool. It houses shower rooms, lockers, a weight room, offices and meeting rooms.

A middle school for seventh and eighth grade girls was established in September 1976.   Beginning in 1995, sixth grade students were admitted.  The middle school provides an excellent academic preparation for students who wish to continue their education in a college preparatory high school.

Over the 100 years of Immaculate Heart's history, there have been many changes as the school has responded to the ever emerging needs of young women living in a complex society and a fast-paced world. However, the school has remained true to its philosophy and mission, with great pride in its heritage and deep reverence for its traditions.