The seminary finds its roots from the Missionary Training Institute, a school established by A.B. Simpson to train missionaries for world service. The school eventually became Nyack College, and the seminary stemmed out of its graduate program, founded in 1960 as the Jaffray School of Missions. In 1974, the program was redesigned and subsequently renamed to the Alliance School of Theology and Missions. It took its current name in 1979, and was first accredited in 1990 by the Commission on Accrediting of the Association of Theological Schools in the United States and Canada.
The seminary offers a variety of graduate degrees including M.A. in intercultural studies or biblical literature, M.P.S., M.Div., and D.Min. In addition to the main campus in Nyack, there is a large satellite campus located in Manhattan, and an extension in Puerto Rico. The 2012 enrollment was approximately 800 students.