California Theological Seminary was founded as Assemblies of God LA Theological College in 1988 for the purpose of training Pentecostal Christian ministers, and the first president, Dr. & Rev. Jae Sun Lee, and the first dean, Rev. Sung Ho Yoon, took office. In 1999, it was approved by the California State Board of Education as a theological school that can award a bachelor's degree (B.A.), master's degrees (M.A., M.Div.), and a doctoral degree (Ph.D.).

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From 2000, the seminaries in each region (LA, New York, Chicago, Dallas) under the A/G Korean District were integrated into the 'Assemblies of God Evangel Theological Seminary', and Dr. & Rev. Ki Hong Kim was inaugurated as president and Rev. Nam Soo Kim was inaugurated as chairman of board. In June of that year, the first integrated graduation ceremony was held at New York Evangel Theological Seminary. Since 2011, the seminaries that had been integrated were changed to separate operations for each region (LA, New York, Chicago, Hawaii), and Dr. & Rev. Young Gil Kim took office as president of the LA Evangel Theological Seminary.

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In 2013, the school name was changed to “California Theological Seminary (CTS)”, and in 2017, chairman of board Rev. Kim Geon Sam, president Dr. & Rev. Yong Ung Ji, and dean Dr. & Rev. Chang Su Eim took office. In the same year, the scope of degree awards was reduced to B.A., M. Div., and M.A. in accordance with changes in the state government's regulations. In July 2018, CTS received approval from the federal government to issue I-20 to foreign students wishing to enroll in master's programs, but stopped recruiting international students after the Coronavirus Pandemic.

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In May 2019, Rev. Sang Eun Sim was inaugurated as the new president, and in July, Elder Kenneth K Park was elected as chairman of board. Currently, our school is striving to train faithful ministers with the goal of 'building ministers equipped with spirituality and character.'