In addition to its 56 parish churches, the diocese oversees 41 schools and three general hospitals, plus one disabled and five ethnic ministry centers.

The Catholic presence in present-day Orange County dates to the 1776 founding of Mission San Juan Capistrano by Junipero Serra and the Franciscan order.

Gregory XVI set the episcopal see at present-day San Diego in Alta California.

Pope Pius IX split the Diocese of Monterey in 1853, erecting the Metropolitan Archdiocese of San Francisco.

[4] St. Boniface, the oldest continually operating Catholic church in Orange County, was dedicated in Anaheim in 1872.

Johnson died in 1986 and Pope John Paul II named Bishop Norman Francis McFarland of the Diocese of Reno as his replacement that same year.

John Paul II named Bishop Tod David Brown from the Diocese of Boise as McFarland's replacement.

[11] The diocese grew rapidly as the local population swelled with Catholic immigrants from Vietnam, the Philippines, and Latin America.

In November 2011, the diocese purchased the Crystal Cathedral in Garden Grove, California, in bankruptcy court from Robert Schuller Ministries.

The Holy See named Bishop Kevin Vann of the Diocese of Fort Worth to succeed him.

In 2005, Bishop Brown apologized to 87 victims of sexual abuse by diocesan clergy and announced a settlement of $100 million, following two years of mediation.

The perpetrators included 31 priests, ten lay people, two nuns, and one religious brother.

[17] In October 2007, Judge Gail Andler opened a contempt of court hearing on Brown regarding John Urell, a diocese official responsible for managing sexual abuse accusations.

However, with the onset of the Catholic sexual abuse scandal in the diocese, Brown deemed it "inappropriate" then to raise funds for a new cathedral.

In 2014, the diocese announced a $72 million plan to renovate the cathedral building to meet Catholic liturgy requirements while maintaining its architectural qualities.