Horton has taught apologetics and theology at Westminster Seminary California since 1998. In addition to his work at the seminary, he is host of the White Horse Inn, a nationally syndicated, weekly radio talk-show exploring issues of Reformation theology in American Christianity. He is also the editor-in-chief of Modern Reformation magazine. He was formerly the president of Christians United for Reformation (CURE), which later merged to become the Alliance of Confessing Evangelicals (ACE). From 2001 to 2004 Horton served as the president of ACE, but is now no longer affiliated with the organization. Being Reformed, Horton is a covenant theologian, and holding to Presbyterian ecclesiology, he is an advocate of infant baptism.