The first mission buildings were made of logs with thatched roofs. Later construction was adobe.
There were four churches built at Santa Barbara, counting the original temporary chapel, before the current building was built and completed in 1820. Today's church is 161 feet long, 42 feet high and 27 feet wide and its walls are six feet thick. The original church had only one tower, but a second was added in 1833. These matching twin towers are 87 feet tall.
The sandstone facade of the church was designed after an ancient Latin temple in pre-Christian Rome. Father Antonio Ripoll copied the design from a Roman architecture book brought by the Franciscans. The sandstone came from the Santa Barbara area. Building started in 1815 and finished in 1820.
Because of its continuous occupation by the Franciscans, the mission today remains much as it was when it was built. However, the mission building suffered a lot of damage in an earthquake in 1925. It took two years and $400,000 to restore it. Later, a chemical reaction in the restoration materials weakened the structure, and the front of the church had to be rebuilt in 1950.