Three Bible schools were brought together to form Southwestern Bible Institute. The first, known as Southwestern Bible School, was established at Enid, Oklahoma in 1927 under the leadership of the Reverend P. C. Nelson. The second, Shield of Faith Bible Institute, was founded in Amarillo, Texas, in 1931 under the direction of the Reverend Guy Shields. It included not only a Bible school, but also a grade school and high school. The third, which was operated as Southern Bible College in connection with the Richey Evangelistic Temple, began at Goose Creek, Texas in 1931. It was started by Reverend J. T. Little in Trinity Tabernacle and later moved to Houston in 1933. The school's name was then changed to Southern Bible Institute.
The Bible school division of Shield of Faith Bible Institute was moved to Fort Worth in 1935. The high school division was transferred the following year. In 1940, a merger resulted in Southern Bible Institute, moving to Fort Worth. The combined school, operating as South Central Bible Institute, came under the ownership and direction of the Texas District Council of the Assemblies of God.
The school in Enid merged with South Central in 1941, at which time the name was changed to Southwestern Bible Institute. In 1943, the institute was moved to its present facilities in Waxahachie, Texas.
During the 1944-45 term, a junior college curriculum was added. The Junior College Division soon accounted for about half of enrollment.
Southwestern Bible Institute became a regional school in 1954. At that time seven districts of the Assemblies of God--Arkansas, Louisiana, New Mexico, North Texas, Oklahoma, South Texas and West Texas--owned and operated the school. In 1969, the Rocky Mountain District, composed of Colorado and Utah, was admitted to the Region. The Mississippi District was then added to the Region in 1979. In 1980, the Rocky Mountain District voted to withdraw from the Southwestern Region and to remain neutral.
The proposal to change the name was ratified by all seven Districts, and the name became Southwestern Assemblies of God College. In 1963, the upper two years of the College were renamed Southwestern College of the Bible. In 1968, the separation of the divisions of the College was made more complete, and the Junior College was designated Southwestern Junior College of the Assemblies of God. In 1987 the two divisions were reunited.
Beginning in the early nineties, the university experienced phenomenal enrollment increases. From 596 students in the fall of 1991, enrollment grew to 1492 students in 1997. Along with the enrollment increase, opportunities to expand the curriculum and programs developed. In December 1994, the Board of Regents unanimously approved the name change to Southwestern Assemblies of God University to more accurately reflect its purpose and mission as a Bible university of theological and professional studies.
In 1996, SAGU expanded to include a graduate school.
In 2004, the academic divisions of the university realigned into two colleges, the College of Bible & Church Ministries and the College of Arts & Professions. Both colleges maintain Bible-based curriculum to fulfill the mission of SAGU.
Since 2000, SAGU has added 24 new academic programs, bringing the total to more than 60 programs. Additionally, under the direction of President Kermit Bridges, the campus continues to grow. In 2006-2007, Teeter and Bridges Halls were added. They were followed by the new Alton Garrison Student Wellness Center in 2009.
Amidst the physical expansion, SAGU experienced consecutive record enrollments Fall 2007 through Fall 2010 reaching a milestone of 2,064.